Add CI readiness skill

[noencke]

This adds a skill to the repo which checks whether a branch is ready to be pushed to CI without obvious problems. This skill is meant to catch the annoying things you forget to do, like format, lint, policy check, and which will cause your CI build to fail. This is otherwise not reviewing the contents of the PR. There are two steps:

1. A hardcoded script which runs all the low hanging fruit (format, policy, etc.). This should complete in under 10 seconds.
2. An LLM reasoning step which looks at more complicated things like, "This package changed, and it changed an API, and it's a dependency of the @fluid-framework package, so you'll need to build API extractor in that package as well". This step can optionally run tests for changed packages, but won't unless instructed to. The skill will prompt the user at the start with "how strong" of a validation they'd like.

The hardcoded script portion could also become a git push hook or similar, if we like.

[github-actions]

🔗 No broken links found! ✅

Your attention to detail is admirable.

linkcheck output

> fluid-framework-docs-site@0.0.0 ci:check-links /home/runner/work/FluidFramework/FluidFramework/docs
> start-server-and-test "npm run serve -- --no-open" 3000 check-links

1: starting server using command "npm run serve -- --no-open"
and when url "[ 'http://127.0.0.1:3000' ]" is responding with HTTP status code 200
running tests using command "npm run check-links"


> fluid-framework-docs-site@0.0.0 serve
> docusaurus serve --no-open

[SUCCESS] Serving "build" directory at: http://localhost:3000/

> fluid-framework-docs-site@0.0.0 check-links
> linkcheck http://localhost:3000 --skip-file skipped-urls.txt

Crawling...

Stats:
  272202 links
    1863 destination URLs
    2108 URLs ignored
       0 warnings
       0 errors