docs: add docker fallback for hugo and markdownlint

[nginx-jack]

Proposed changes

Adds a docker fallback for hugo and markdownlint. The goal is to make it possible to contribute to documentation without needing to install additional tooling (expect docker!).

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes NA
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (7ae5a19) 52.09% compared to head (70bf420) 52.09%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4747   +/-   ##
=======================================
  Coverage   52.09%   52.09%           
=======================================
  Files          59       59           
  Lines       17033    17033           
=======================================
  Hits         8873     8873           
  Misses       7862     7862           
  Partials      298      298           

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[ADubhlaoich]

LGTM but you should be aware that NGINX Ingress Controller does not use conventional commits.