add docs upstream validation workflow

[dvdksn]

Signed-off-by: David Karlsson 35727626+dvdksn@users.noreply.github.com

What I did

added a gha workflow that verifies that the reference docs don't contain broken links etc

Related issue

(not mandatory) A picture of a cute animal, if possible in relation to what you did

🐥

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (b8773ad) 57.42% compared to head (93137e7) 57.42%.
Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #11113      +/-   ##
==========================================
- Coverage   57.42%   57.42%   -0.01%     
==========================================
  Files         129      129              
  Lines       11274    11285      +11     
==========================================
+ Hits         6474     6480       +6     
- Misses       4168     4173       +5     
  Partials      632      632              

see 7 files with indirect coverage changes

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[dvdksn]

hey @glours and @ndeloof, I added this new workflow that gives you some validation (check for broken links etc) in your CI. We have the same in Buildx and BuildKit, and since we vendor docs from this repo too I thought it would be good to add here

[glours]

LGTM