Add workflow to check checklist and PR template

[josh-wong]

Description

This PR adds a workflow to check if items in a checklist have been checked and then leaves a comment about whether the check was a success or a failure.

Related issues and/or PRs

N/A

Changes made

• Created a workflow file that uses an action to check if items in an opened or edited pull request have been checked.
• Changed the Checklist heading from Markdown to HTML, and added an id value to link to that section in comments about the workflow failing.
• Added a PR template.

Checklist

The following is a best-effort checklist. If any items in this checklist aren't applicable to this PR, add N/A after each item.

Documentation

• I have updated the side navigation as necessary. N/A
• I have updated the documentation to reflect the changes. N/A
• I have documented or updated any remaining open issues linked to this PR in GitHub, Obsidian, etc. N/A

Build, deploy, and test

• I have merged and published any dependent changes in other PRs. N/A
• I have commented my code, particularly in hard-to-understand areas. N/A
• I have checked that my changes look as expected on a locally built version of the docs site. N/A
• My changes generate no new warnings.

[github-actions]

All items in the checklist have been checked🎉