docs: add initial CHANGELOG.md using Keep a Changelog standard

[AaineeSinha]

Closes #10. Added a baseline CHANGELOG.md file to the repository root adhering to the Keep a Changelog standard.

[rosspeili]

Thanks for adding this @AaineeSinha, the setup looks good and is exactly what we needed to get started.

Before merge, could you tweak a couple things in the same PR?

• CHANGELOG.md, keep the structure, but add a short note that we’re still pre-release and versioned entries will come later (you can backfill old PRs in a short list if you want but not mandatory for this PR).
• README.md, link to CHANGELOG.md in the docs section.
• CONTRIBUTING.md, one line that the changelog exists; we’ll ask for [Unreleased] updates once we start doing releases.

That’s it, thanks again, and welcome to Rooms <3

[AaineeSinha]

Thanks for the warm welcome, @rosspeili! I've gone ahead and addressed all your feedback: I added the pre-release note to CHANGELOG.md, linked the changelog in the README.md documentation library, and updated the PR instructions in CONTRIBUTING.md. Let me know if everything looks good on your end now!

[rosspeili]

Thanks for the quick follow-up @AaineeSinha, README and CONTRIBUTING look good, and the pre-release note is what we wanted.

One small fix: CHANGELOG.md has escaped markdown (\#, \##, etc.) so headings won’t render on GitHub. Could you remove those backslashes and keep the pre-release note? The link formatting from your first commit was fine if you want to bring that back too.

Once that’s in, good to merge from my side. Thanks again!

[AaineeSinha]

I've updated the branch and removed the escaping backslashes from the markdown headers so everything should render correctly now.

[rosspeili]

Perfect, CHANGELOG renders correctly now, and README/CONTRIBUTING look good. Merging this, thanks for sticking with the review rounds and again, welcome to Rooms! <3