Fix editing, typos and grammatical errors (#6207)

1. The current version is ~at~ on the Arduino website
2. Start Arduino and open _the_ Preferences window
3. Enter ```https://arduino.esp8266.com/stable/package_esp8266com_index.json``` into _the_ *Additional Board Manager URLs* field
4. The current version is ~at~ on the Arduino website
5. [PlatformIO](https://platformio.org?utm_source=github&utm_medium=arduino-esp8266) is an open source ecosystem for IoT
development with _a_ ~cross platform~ cross-platform build system, library manager and full support
6. [ESP8266 Community Forum](https://www.esp8266.com/u/arduinoanswers) is a ~well established~ well-established community
7. or just want to discuss how to approach a problem, (removed extra space after 'problem')
8. when encountering an issue ~which~ that happens at run time
9. attach _the_ serial output
10. Check out the list of issues ~which~ that are easy to fix
11. It is distributed under _the_ MIT license.
12. It is distributed under _the_ MIT license.

Author: race2infinity

README.md

@@ -28,9 +28,9 @@ ESP8266 Arduino core comes with libraries to communicate over WiFi using TCP and
 
 Starting with 1.6.4, Arduino allows installation of third-party platform packages using Boards Manager. We have packages available for Windows, Mac OS, and Linux (32 and 64 bit).
 
-- Install the current upstream Arduino IDE at the 1.8.7 level or later. The current version is at the [Arduino website](https://www.arduino.cc/en/main/software).
-- Start Arduino and open Preferences window.
-- Enter ```https://arduino.esp8266.com/stable/package_esp8266com_index.json``` into *Additional Board Manager URLs* field. You can add multiple URLs, separating them with commas.
+- Install the current upstream Arduino IDE at the 1.8.7 level or later. The current version is on the [Arduino website](https://www.arduino.cc/en/main/software).
+- Start Arduino and open the Preferences window.
+- Enter ```https://arduino.esp8266.com/stable/package_esp8266com_index.json``` into the *Additional Board Manager URLs* field. You can add multiple URLs, separating them with commas.
 - Open Boards Manager from Tools > Board menu and install *esp8266* platform (and don't forget to select your ESP8266 board from Tools > Board menu after installation).
 
 #### Latest release [![Latest release](https://img.shields.io/github/release/esp8266/Arduino.svg)](https://github.com/esp8266/Arduino/releases/latest/)
@@ -41,7 +41,7 @@ Documentation: [https://arduino-esp8266.readthedocs.io/en/2.5.2/](https://arduin
 ### Using git version (basic instructions)
 [![Linux build status](https://travis-ci.org/esp8266/Arduino.svg)](https://travis-ci.org/esp8266/Arduino)
 
-- Install the current upstream Arduino IDE at the 1.8 level or later. The current version is at the [Arduino website](https://www.arduino.cc/en/main/software).
+- Install the current upstream Arduino IDE at the 1.8 level or later. The current version is on the [Arduino website](https://www.arduino.cc/en/main/software).
 - Go to Arduino directory
   - For Mac OS X, it is `Arduino.app` showing as the Arduino icon.  
     This location may be your `~/Downloads`, `~/Desktop` or even `/Applications`.
@@ -71,7 +71,7 @@ python get.py
 ### Using PlatformIO
 
 [PlatformIO](https://platformio.org?utm_source=github&utm_medium=arduino-esp8266) is an open source ecosystem for IoT
-development with cross platform build system, library manager and full support
+development with a cross-platform build system, library manager and full support
 for Espressif (ESP8266) development. It works on the popular host OS: macOS, Windows,
 Linux 32/64, Linux ARM (like Raspberry Pi, BeagleBone, CubieBoard).
 
@@ -95,7 +95,7 @@ Documentation for latest development version: https://arduino-esp8266.readthedoc
 
 ### Issues and support ###
 
-[ESP8266 Community Forum](https://www.esp8266.com/u/arduinoanswers) is a well established community for questions and answers about Arduino for ESP8266. If you need help, have a "How do I..." type question, have a problem with a 3rd party lib not hosted in this repo, or just want to discuss how to approach a problem , please ask there.
+[ESP8266 Community Forum](https://www.esp8266.com/u/arduinoanswers) is a well-established community for questions and answers about Arduino for ESP8266. If you need help, have a "How do I..." type question, have a problem with a 3rd party lib not hosted in this repo, or just want to discuss how to approach a problem, please ask there.
 
 If you find the forum useful, please consider supporting it with a donation. <br />
 [![Donate](https://img.shields.io/badge/paypal-donate-yellow.svg)](https://www.paypal.com/webscr?cmd=_s-xclick&hosted_button_id=4M56YCWV6PX66)
@@ -106,7 +106,7 @@ Please provide as much context as possible, as well as the information requested
 
 - ESP8266 Arduino core version which you are using (you can check it in Boards Manager)
 - your sketch code; please wrap it into a code block, see [Github markdown manual](https://help.github.com/articles/basic-writing-and-formatting-syntax/#quoting-code)
-- when encountering an issue which happens at run time, attach serial output. Wrap it into a code block, just like the code.
+- when encountering an issue that happens at run time, attach the serial output. Wrap it into a code block, just like the code.
 - for issues which happen at compile time, enable verbose compiler output in the IDE preferences, and attach that output (also inside a code block)
 - ESP8266 development board model
 - IDE settings (board choice, flash size)
@@ -116,7 +116,7 @@ Please provide as much context as possible, as well as the information requested
 
 For minor fixes of code and documentation, please go ahead and submit a pull request.
 
-Check out the list of issues which are easy to fix — [easy issues pending](https://github.com/esp8266/Arduino/issues?q=is%3Aopen+is%3Aissue+label%3A%22level%3A+easy%22). Working on them is a great way to move the project forward.
+Check out the list of issues that are easy to fix — [easy issues pending](https://github.com/esp8266/Arduino/issues?q=is%3Aopen+is%3Aissue+label%3A%22level%3A+easy%22). Working on them is a great way to move the project forward.
 
 Larger changes (rewriting parts of existing code from scratch, adding new functions to the core, adding new libraries) should generally be discussed by opening an issue first.
 
@@ -134,9 +134,9 @@ Espressif SDK included in this build is under Espressif MIT License.
 
 ESP8266 core files are licensed under LGPL.
 
-[SPI Flash File System (SPIFFS)](https://github.com/pellepl/spiffs) written by Peter Andersson is used in this project. It is distributed under MIT license.
+[SPI Flash File System (SPIFFS)](https://github.com/pellepl/spiffs) written by Peter Andersson is used in this project. It is distributed under the MIT license.
 
-[umm_malloc](https://github.com/rhempel/umm_malloc) memory management library written by Ralph Hempel is used in this project. It is distributed under MIT license.
+[umm_malloc](https://github.com/rhempel/umm_malloc) memory management library written by Ralph Hempel is used in this project. It is distributed under the MIT license.
 
 [SoftwareSerial](https://github.com/plerup/espsoftwareserial) library and examples written by Peter Lerup. Distributed under LGPL 2.1.