ci: add automated thank you workflow for merged PRs

[shivansh-gohem]

This PR introduces a new GitHub Action workflow to automate contributor appreciation. It listens for merged Pull Requests and uses the GitHub Search API to determine if the author is a first-time contributor or a returning contributor, leaving a customized thank-you comment accordingly

[Ayushmore1214]

@shivansh-gohem Dropped some suggestions!

[shivansh-gohem]

Hi @Ayushmore1214, thank you again for the great feedback! All requested changes have been addressed and pushed

[shivansh-gohem]

I ran a test on my fork, and the maintainer-skip logic worked perfectly! Since I am the OWNER of my fork, the bot correctly identified my association and gracefully exited without commenting. I've attached the screenshot of the Action logs below as proof

[Ayushmore1214]

@Warashi Since the token permission blocks us, parsing MAINTAINERS.md is definitely the cleanest workaround

[Warashi]

@Ayushmore1214 It works, but it's not recommended since MAINTAINERS.md is intended for humans, not machines.

[Warashi]

IMO, to implement this feature stably, we must manage the maintainer list in a machine-readable format, such as JSON.

[Ayushmore1214]

@Warashi 100% agree JSON file works!

[shivansh-gohem]

great catch @Warashi! I didn't realize the default token was blind to private members. I totally agree that a machine-readable format is the way to go. I'll push an update shortly that adds a MAINTAINERS.json file and updates the script to read from it using Node's fs module!

[shivansh-gohem]

@Warashi @Ayushmore1214 i have adressed the issue you raised !! please review!!