fix: pass GitHub token to setup-bun to avoid rate limits

[peloyeje]

Summary

• Pass github_token input (or fallback github.token) to the setup-bun action
• Prevents 403 rate limit errors when fetching Bun release tags from GitHub API on shared runners

Problem

The setup-bun action fetches Bun release tags from the GitHub API. Without an authenticated token, it hits rate limits (403 error) when running from shared GitHub Actions runners:

Error: API rate limit exceeded for <IP>. (But here's the good news: Authenticated requests get a higher rate limit. Check out the documentation for more details.)

Solution

Pass the user-provided github_token input to setup-bun, falling back to ${{ github.token }} when not provided. This provides authenticated API access without requiring any changes from users.