Add CONTRIBUTING.md with reference to p5.js contribution guide

[Sana9058]

This PR adds a CONTRIBUTING.md file to the repository that links to the main p5.js contribution guide,
making contribution guidelines more discoverable and aligned with GitHub recommendations.

Closes #1079

[Piyushrathoree]

@Sana9058 hey hi you can also add how to setup this repo. in the PR

[Sana9058]

@Piyushrathoree Thanks for the suggestion! I can add a brief local setup section to CONTRIBUTING.md. I’ll update the PR shortly.

[Sana9058]

@Piyushrathoree Thanks for the suggestion! I've added a "Local Development Setup" section to CONTRIBUTING.md with steps to clone the repo, install dependencies, and start the dev server. Please let me know if you'd like anything else added.

[ksen0]

Hi @Sana9058 ! Thanks for your interest in working on this. However, this PR is currently incomplete - more importantly, the original issue is in discussion. It has not yet been marked ready for work, or assigned. Please read carefully through the contributor guidelines before future PRs:

You should not “jump the queue” by filing a PR for an issue that either someone else has indicated willingness to submit a contribution or has already been assigned to someone else. We will always prioritize the “first assigned, first serve” order for accepting code contributions for an issue. If you file a PR for an issue while someone else is still working on the same issue, your PR will likely be closed.

Thanks so much for understanding.