docs: fix coverage badge and missing index in README

Author: mtrezza

README.md

@@ -2,7 +2,7 @@
 
 [![Build Status](https://github.com/parse-community/parse-server-api-mail-adapter/workflows/ci/badge.svg?branch=main)](https://github.com/parse-community/parse-server-api-mail-adapter/actions?query=workflow%3Aci+branch%3Amain)
 [![Snyk Badge](https://snyk.io/test/github/parse-community/parse-server-api-mail-adapter/badge.svg)](https://snyk.io/test/github/parse-community/parse-server-api-mail-adapter)
-[![Coverage](https://codecov.io/gh/parse-community/parse-server-api-mail-adapter/branch/main/graph/badge.svg)](https://codecov.io/gh/parse-community/parse-server-api-mail-adapter)
+[![Coverage](https://codecov.io/gh/parse-community/parse-server-api-mail-adapter/branch/alpha/graph/badge.svg)](https://codecov.io/gh/parse-community/parse-server-api-mail-adapter)
 [![auto-release](https://img.shields.io/badge/%F0%9F%9A%80-auto--release-9e34eb.svg)](https://github.com/parse-community/parse-dashboard/releases)
 
 [![Node Version](https://img.shields.io/badge/nodejs-12,_14,_16,_18-green.svg?logo=node.js&style=flat)](https://nodejs.org)
@@ -39,6 +39,7 @@ The Parse Server API Mail Adapter enables Parse Server to send emails using any
 - [Supported APIs](#supported-apis)
   - [Providers](#providers)
     - [Example for Mailgun](#example-for-mailgun)
+    - [Example for AWS Simple Email Service](#example-for-aws-simple-email-service)
   - [Custom API](#custom-api)
 - [Need help?](#need-help)