ci: add workflow to auto-update homebrew tap on release

[vedansh-agarwal]

Description

Adds a GitHub Actions workflow that automatically updates the Homebrew tap
(Zackriya-Solutions/homebrew-meetily) whenever a new release is published.

On each non-draft, non-prerelease release: published event, the workflow:

1. Downloads the _aarch64.dmg asset
2. Computes its SHA256
3. Checks out the tap repo and updates the version and sha256 fields in Casks/meetily.rb using sed
4. Commits and pushes the bump with an attribution link back to the triggering release

This eliminates the manual step of updating the tap after each release.

Related Issue

N/A — this is a self-contained automation improvement.

Type of Change

• Bug fix
• New feature
• Documentation update
• Performance improvement
• Code refactoring
• Other (CI/CD automation — new workflow file only, no source code changes)

Testing

• Manual testing performed
• All tests pass

Tested end-to-end on a fork (vedansh-agarwal/meetily → vedansh-agarwal/homebrew-meetily):
created a test release with a renamed DMG asset, confirmed the workflow ran successfully and
committed the correct version and SHA256 to the tap.

Documentation

• Documentation updated
• No documentation needed

The workflow file is self-documenting.

Checklist

• Code follows project style
• Self-reviewed the code
• Added comments for complex code
• Updated README if needed
• Branch is up to date with devtest
• No merge conflicts

Screenshots (if applicable)

N/A — workflow file addition only.

Additional Notes

One manual step required by the repo maintainer: a fine-grained PAT named
HOMEBREW_TAP_TOKEN must be added to this repo's secrets with Contents: Read and Write
permission scoped to Zackriya-Solutions/homebrew-meetily. Without it the workflow will
fail at the push step.

This PR is a companion to a separate PR on the tap repo itself
(Zackriya-Solutions/homebrew-meetily) which updates the cask to v0.3.0 and cleans up
the obsolete backend formula.