Update PR template to be more similar to the one of PowerShell but still distinguish where necessary (#1077)

Author: bergmeister

.github/PULL_REQUEST_TEMPLATE.md

@@ -4,13 +4,11 @@
 
 ## PR Checklist
 
-Note: Tick the boxes below that apply to this pull request by putting an `x` between the square brackets. Please mark anything not applicable to this PR `NA`.
-
-- [ ] PR has a meaningful title
-    - [ ] Use the present tense and imperative mood when describing your changes
-- [ ] Summarized changes
-- [ ] User facing documentation needed
-- [ ] Change is not breaking
-- [ ] Make sure you've added a new test if existing tests do not effectively test the code changed
-- [ ] This PR is ready to merge and is not work in progress
-    - If the PR is work in progress, please add the prefix `WIP:` to the beginning of the title and remove the prefix when the PR is ready
+- [ ] [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)
+- [ ] [Change is not breaking](https://github.com/PowerShell/PowerShell/blob/master/.github/CONTRIBUTING.md#making-breaking-changes)
+- [ ] [Make sure all `.cs`, `.ps1` and `.psm1` files have the correct copyright header](https://github.com/PowerShell/PowerShell/blob/master/.github/CONTRIBUTING.md#pull-request---submission)
+- [ ] Make sure you've added a new test if existing tests do not effectively test the code changed and/or updated documentation
+- [ ] This PR is ready to merge and is not [Work in Progress](https://github.com/PowerShell/PowerShell/blob/master/.github/CONTRIBUTING.md#pull-request---work-in-progress).
+    - If the PR is work in progress, please add the prefix `WIP:` to the beginning of the title and remove the prefix when the PR is ready.