docs: link examples index from Readme (Fixes #1037)

[leno23]

Summary

• Link docs/list-of-examples.md from the documentation index in docs/Readme.md.
• Note that examples/ programs are built and run in CI.
• Add the custom-main configuration example to the examples list.

Fixes #1037

Test plan

• Docs-only change; verified links resolve to existing examples/*.cpp files.

Made with Cursor

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.26%. Comparing base (69e0473) to head (32789ac).
⚠️ Report is 2 commits behind head on devel.

Additional details and impacted files

@@           Coverage Diff           @@
##            devel    #3135   +/-   ##
=======================================
  Coverage   91.26%   91.26%           
=======================================
  Files         204      204           
  Lines        8905     8905           
=======================================
  Hits         8127     8127           
  Misses        778      778           

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