Update documentation to make it clear where to find llms.txt

[csvance]

Add a relative link to llms.txt in generated HTML documentation.

[codecov-commenter]

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.96%. Comparing base (bd65a33) to head (610f8e5).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #109   +/-   ##
=======================================
  Coverage   90.96%   90.96%           
=======================================
  Files           7        7           
  Lines         531      531           
=======================================
  Hits          483      483           
  Misses         48       48           

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