ci: send slack notification for broken links

[ccmao1130]

Seems like Slack notifications stopped working after #3317

[codspeed-hq]

CodSpeed Performance Report

Merging #3742 will degrade performances by 42.04%

_{Comparing slack-broken-link (88c6f0a) with main (d53e64b)}

Summary

❌ 1 regressions
✅ 26 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
❌	test_iter_rows_first_row[100 Small Files]	175 ms	301.9 ms	-42.04%

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.78%. Comparing base (3462732) to head (88c6f0a).
Report is 9 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3742      +/-   ##
==========================================
+ Coverage   77.65%   77.78%   +0.13%     
==========================================
  Files         731      733       +2     
  Lines       92379    92662     +283     
==========================================
+ Hits        71734    72075     +341     
+ Misses      20645    20587      -58     

see 30 files with indirect coverage changes