docs: improve contributing and pull request documentation

[caseyisonit]

Description

This PR introduces:

• a PULL_REQUESTS.md file that outlines our PR submission and review process. It also includes etiquette guidelines and conflict resolution notes.
• improvements to our CONTRIBUTING.md file to clean up the structure and provide more clarity for contributors to our process.
• PR template cleanup to reduce redundancy in completing it

The goal of this PR is to be COLLABORATIVE. Nothing is set in stone and is absolutely up for discussion and amendment. All reviewers are encouraged to add comments and questions to have discussion.

Related issue(s)

• SWC-764

How has this been tested?

• Read Contributing doc

• Read Pull requests doc

Checklist

• If my change required a change to the documentation, I have updated the documentation in this pull request.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have reviewed at the Accessibility Practices for this feature, see: Aria Practices

Best practices

This repository uses conventional commit syntax for each commit message; note that the GitHub UI does not use this by default so be cautious when accepting suggested changes. Avoid the "Update branch" button on the pull request and opt instead for rebasing your branch against main.

[changeset-bot]

⚠️ No Changeset found

Latest commit: 3fbd28a

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[github-actions]

Branch preview

• Documentation Site
• Storybook

Review the following VRT differences

When a visual regression test fails (or has previously failed while working on this branch), its results can be found in the following URLs:

• Spectrum | Light | Medium | LTR
• Spectrum | Dark | Large | RTL
• Express | Light | Medium | LTR
• Express | Dark | Large | RTL
• Spectrum-two | Light | Medium | LTR
• Spectrum-two | Dark | Large | RTL
• High Contrast Mode | Medium | LTR

If the changes are expected, update the current_golden_images_cache hash in the circleci config to accept the new images. Instructions are included in that file.
If the changes are unexpected, you can investigate the cause of the differences and update the code accordingly.

[github-actions]

Tachometer results

Currently, no packages are changed by this PR...

[najikahalsema]

This looks great so far! I have one request but otherwise thank you so much for your work on this!

[pfulton]

Overall, I think this looks good. I just noticed a few things that I wanted to suggest! I'm fine with merging, but will reserve an approval until others are able to review, too.

[najikahalsema]

My pass has... passed. Take a look!

[Rajdeepc]

Good start! Thank you for doing this!

[najikahalsema]

Looks GREAT! One little nit, not a blocker, but while i love the emojis in the sev classification table, they also do put the numbers on a newline 😭

I just thought you'd like to know since i wasn't originally reading this outside of the diff.

[nikkimk]

LGTM (Lofty Goal Totally Met)