docs: improve contributing and pull request documentation

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,4 +1,5 @@
 <!--- Provide a general summary of your changes in the Title above -->
+<!--- PR titles should follow conventional commit and should include commit type as defined in in the PULL_REQUESTS guide -->
 
 ## Description
 
@@ -7,57 +8,45 @@
 ## Related issue(s)
 
 <!---
-    This project only accepts pull requests related to open issues
-
     - If suggesting a new feature or change, please discuss it in an issue first.
     - If fixing a bug, there should be an issue describing it with steps to reproduce.
+    - If you're Adobe internal, add a Jira ticket number but do NOT link directly to Jira.
 -->
 
--
-
-## Motivation and context
-
-<!--- Why is this change required? What problem does it solve? -->
+-   fixes [Issue Number]
 
 ## How has this been tested?
 
 <!--- Please describe in detail how you tested your changes. -->
 <!--- Include details of your testing environment, and the tests you ran to see how your change affects other areas of the code, etc. -->
 
--   [ ] _Test case 1_
+-   [ ] _Descriptive Test Statement_
+
     1. Go here
     2. Do this
--   [ ] _Test case 2_
+    3. Expect this
 
+-   [ ] _Descriptive Test Statement_
     1. Go here
     2. Do this
+    3. Expect this
+
+Polypane review:
 
 -   [ ] Did it pass in Desktop?
--   [ ] Did it pass in Mobile?
--   [ ] Did it pass in iPad?
+-   [ ] Did it pass in (emulated) Mobile?
+-   [ ] Did it pass in (emulated) iPad?
 
 ## Screenshots (if appropriate)
 
-## Types of changes
-
-<!--- What types of changes does your code introduce? Put an `x` in all the boxes that apply: -->
-
--   [ ] Bug fix (non-breaking change which fixes an issue)
--   [ ] New feature (non-breaking change which adds functionality)
--   [ ] Breaking change (fix or feature that would cause existing functionality to change)
--   [ ] Chore (minor updates related to the tooling or maintenance of the repository, does not impact compiled assets)
-
 ## Checklist
 
 <!--- Go over all the following points, and put an `x` in all the boxes that apply.  If you're unsure about any of these, don't hesitate to ask. We're here to help! -->
 
--   [ ] I have signed the [Adobe Open Source CLA](http://opensource.adobe.com/cla.html).
--   [ ] My code follows the code style of this project.
--   [ ] If my change required a change to the documentation, I have updated the documentation in this pull request.
--   [ ] I have read the **[CONTRIBUTING](<(https://github.com/adobe/spectrum-web-components/blob/main/CONTRIBUTING.md)>)** document.
--   [ ] I have added tests to cover my changes.
--   [ ] All new and existing tests passed.
+-   [ ] I have read the **[CONTRIBUTING](<(https://github.com/adobe/spectrum-web-components/blob/main/CONTRIBUTING.md)>)** and **[PULL_REQUESTS](<(https://github.com/adobe/spectrum-web-components/blob/main/PULL_REQUESTS.md)>)** documents.
 -   [ ] I have reviewed at the Accessibility Practices for this feature, see: [Aria Practices](https://www.w3.org/TR/wai-aria-practices/)
+-   [ ] I have added tests to cover my changes.
+-   [ ] I have ensured documentation covers my changes.
 
 ## Best practices