Add workflow to detect broken links in doc

[sridhargaddam]

This PR adds a GitHub workflow that validates any broken links in the Sail Operator docs. It is scheduled to run every Sunday at midnight.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.03%. Comparing base (bbc577d) to head (f7ac192).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #611      +/-   ##
==========================================
- Coverage   74.43%   74.03%   -0.40%     
==========================================
  Files          40       40              
  Lines        2511     2511              
==========================================
- Hits         1869     1859      -10     
- Misses        554      561       +7     
- Partials       88       91       +3     

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[sridhargaddam]

The tests are failing with the following error :(

 Failed to pull image "docker.io/istio/install-cni:1.24.1": failed to pull and unpack image "docker.io/istio/install-cni:1.24.1": failed to copy: httpReadSeeker: failed open: unexpected status code https://registry-1.docker.io/v2/istio/install-cni/manifests/sha256:d241cd11295b7c7af6c1c7e22096db886b07ab1945b4b7b2fe3d7f95ef41b277: 429 Too Many Requests - Server message: toomanyrequests: You have reached your pull rate limit. You may increase the limit by authenticating and upgrading: https://www.docker.com/increase-rate-limit

[luksa]

/retest