Add Playwright Test README for documentation

[JCantu248]

🗣 Description

Add Playwright's README.md

💭 Motivation and context

This is necessary to provide documentation for developers to help understand how to use the tool.

🧪 Testing

N/A, just verify passes markdown linters and documentation is accurate.

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• Changes are limited to a single goal - eschew scope creep!
• All future TODOs are captured in issues, which are referenced in code comments.
• All relevant type-of-change labels have been added.
• I have read the CONTRIBUTING document.
• These code changes follow cisagov code standards.
• All relevant repo and/or project documentation has been updated to reflect the changes in this PR.
• Tests have been added and/or modified to cover the changes in this PR.
• All new and existing tests pass.
• Bump major, minor, patch, pre-release, and/or build versions as appropriate via the bump_version script if this repository is versioned and the changes in this PR warrant a version bump.
• Create a pre-release (necessary if and only if the pre-release version was bumped).

[rapidray12]

Simple documentation update

[chrtorres]

Approved through group review

[nickviola]

LGTM

[cduhn17]

LGTM. I like this kind of breakdown

[schmelz21]

Before we merge, I just need a read-through. Thanks.