ci: add user-doc label checker

[nicecui]

I hereby agree to the terms of the GreptimeDB CLA

What's changed and what's your intention?

PLEASE DO NOT LEAVE THIS EMPTY !!!

In order to catching the imapaction of the PRs to user documentation, label Doc update required or Doc not needed should be added before merging.

If the label Doc update required is added, the doc-issue.yml workflow will add a issue to docs repo.

Checklist

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.

Refer to a related PR or issue link (optional)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (d2f49cb) 85.81% compared to head (168788f) 85.29%.
Report is 2 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2967      +/-   ##
===========================================
- Coverage    85.81%   85.29%   -0.53%     
===========================================
  Files          767      770       +3     
  Lines       123745   123951     +206     
===========================================
- Hits        106193   105725     -468     
- Misses       17552    18226     +674     

[sunng87]

It seems we changed type case of doc updated required, you might want to update this line as well: https://github.com/GreptimeTeam/greptimedb/blob/develop/.github/workflows/doc-issue.yml#L13