Add an example of iterating through pull request changed files in ruby.

I currently got this much done on it myself, however with not knowing ruby much at all I am not sure if I coded it all right. The code lies at https://github.com/Elskom/CI/blob/master/CI.rb. Yes it is formatted like the building a CI server example but with pull request label check for "skip news", and a "Misc/NEWS" entry check for if a new file was added there. I am not sure how I can filter it though to where that check only works with new entry files, not modified or deleted ones unless all of them merged to a single file (like right before a release). I would also love to be able to have my CI read comments from repo /org admins though for things like "I approve this" where the CI then approves the changes and then waits for "merge squashed/rebased/commit". I personally think it would be great to have an example like that tbh. And yes, feel free to use the code I got so far on an example, I don’t mind if you guys even linked to it too. Also I thought those octocat stuff was some sort of photoshopped thing. 🤔

Start by reviewing CI.rb and the existing building-a-CI-server example. Determine how the sample should inspect pull request changed files, distinguish newly added Misc/NEWS entries from modified or deleted files, and handle the requested label and administrator-comment workflow. Done means the Ruby example clearly demonstrates the agreed checks and approval or merge behavior.

索引モデルが issue の本文から書いたものです。