ci: add PR comment and cc reviewers

[Xunzhuo]

What type of PR is this?

What this PR does / why we need it:

Which issue(s) this PR fixes:

We tried a couple of ways to auto request reviews from @envoyproxy/gateway-reviewers, but it failed, and I tried it too today, failed again.

So current way is to add a welcome comment to cc @envoyproxy/gateway-maintainers and @envoyproxy/gateway-reviewers, they should get the ping too.

[Xunzhuo]

demo uestcer/community#191

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (52af65e) 64.38% compared to head (009c2d1) 64.37%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2280      +/-   ##
==========================================
- Coverage   64.38%   64.37%   -0.02%     
==========================================
  Files         112      112              
  Lines       15874    15874              
==========================================
- Hits        10221    10219       -2     
- Misses       5004     5005       +1     
- Partials      649      650       +1     

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[zirain]

I have no objection to this, but not sure this's good to go, @envoyproxy/gateway-maintainers PTAL.

[shawnh2]

i think the comment is quiet long, how about shrinking down to, for example, like:

---

🚀 Thank you for contributing to the Envoy Gateway project! 🚀

Before merging, please ensure to follow the process below:

1. Requesting Reviews:

• cc @envoyproxy/gateway-reviewers team for an initial review.
• After the initial review, reviewers should request the @envoyproxy/gateway-maintainers team for further review.

2. Review Approval:

• Your PR needs to receive at least two approvals.
• At least one approval must come from a member of the gateway-maintainers team.

What's more, you can help expedite the processing of your PR by

• Ensuring you have self-reviewed your work according to the project's Contribution Guidelines.
• If your PR addresses a specific issue, make sure to mention it in the PR description.
• Respond promptly if there are any test failures or suggestions for improvements that we comment on.

[zirain]

BTW, if you really want to add this, please mention that don't use force push like envoy does for better review.

[Xunzhuo]

@shawnh2 I like the idea.

BTW, if you really want to add this, please mention that don't use force push like envoy does for better review.

sure @zirain

[Xunzhuo]

PTAL uestcer/community#191 (comment)

@zirain @qicz @shawnh2

[shawnh2]

lgtm