contribution guidelines: change to say updating changelog is required (#5586)

- Update contribution guidelines to make updating the changelog required
- add a checklist to PR template

Comment by @SteveL-MSFT :
> Everyone should understand that we are always open to feedback and nothing is set in stone. Based on a team discussion, one of the biggest costs for a release is creating the ChangeLog hence updating this document to push it to the contributor most aware of why the changes are being made and ideally how it's useful to end users.

.github/CODEOWNERS

@@ -13,7 +13,7 @@
 # @TravisEz13 @PaulHigin
 
 # Area: Documentation
-# @joeyaiello @TravisEz13
+.github/    @joeyaiello @TravisEz13
 
 # Area: Test
 # @JamesWTruher @TravisEz13 @adityapatwardhan

.github/CONTRIBUTING.md

@@ -129,19 +129,20 @@ Additional references:
   If the changes are related to an existing GitHub issue,
   please reference the issue in PR description (e.g. ```Fix #11```).
   See [this][closing-via-message] for more details.
-* If the change warrants a note in the [changelog](../CHANGELOG.MD)
-  either update the changelog in your pull request or
-  add a comment in the PR description saying that the change may warrant a note in the changelog.
-  New changes always go into the **Unreleased** section.
+
+#### Pull request - Change log
+
+* All PRs must update the [changelog](../CHANGELOG.MD) in your pull request.
+  New changes always go into the **Unreleased** section at the top of the changelog.
   Keeping the changelog up-to-date simplifies the release process for Maintainers.
   An example (with an associated PR #):
 
   ```markdown
-  Unreleased
-  ----------
+  ## Unreleased
 
-  * `Update-Item` now supports `-FriendlyName` (#1234).
+  * `Update-Item` now supports `-FriendlyName` (#1234, @ExampleUser).
   ```
+  Note:  Please add `**Breaking Change**` to the front of the entry in the changelog if the change is [breaking.](#making-breaking-changes)
 
 * Please use the present tense and imperative mood when describing your changes:
     * Instead of "Adding support for Windows Server 2012 R2", write "Add support for Windows Server 2012 R2".

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,8 +1,14 @@
-<!--
+## PR Checklist
 
-If you are a PowerShell Team member, please make sure you choose the Reviewer(s) and Assignee for your PR.
-If you are not from the PowerShell Team, you can leave the fields blank and the Maintainers will choose them for you. If you are familiar with the team, feel free to mention some Reviewers yourself.
+Note: Please mark anything not applicable to this PR `NA`.
+- [ ] [PR has a meaningful title](https://github.com/PowerShell/PowerShell/blob/master/.github/CONTRIBUTING.md#pull-request---submission)
+    - [ ] Use the present tense and imperative mood when describing your changes
+- [ ] [Summarized changes](https://github.com/PowerShell/PowerShell/blob/master/.github/CONTRIBUTING.md#pull-request---submission)
+- [ ] [Update the changelog](https://github.com/PowerShell/PowerShell/blob/master/.github/CONTRIBUTING.md#pull-request---changelog)
+- [ ] User facing [Documentation needed](https://github.com/PowerShell/PowerShell/blob/master/.github/CONTRIBUTING.md#pull-request---submission)
+    - [ ] Issue filed - Issue link:
+- [ ] [Change is not breaking](https://github.com/PowerShell/PowerShell/blob/master/.github/CONTRIBUTING.md#making-breaking-changes)
+- [ ] [Make sure you've added a new test, if existing tests do not effectively test the code changed](https://github.com/PowerShell/PowerShell/blob/master/.github/CONTRIBUTING.md#before-submitting)
+    - [ ] [Add `[feature]` if the change is significant or affectes feature tests](https://github.com/PowerShell/PowerShell/blob/master/docs/testing-guidelines/testing-guidelines.md#requesting-additional-tests-for-a-pr)
 
-For more information about the roles of Reviewer and Assignee, refer to [CONTRIBUTING.md](https://github.com/PowerShell/PowerShell/blob/master/.github/CONTRIBUTING.md).
-
--->
+## PR Summary