fix: "Edit this page" and "View this page" button leads to 404 #2

The "Edit on GitHub" and "View source" buttons on api.pyfenn.org are currently pointing to https://github.com/pyfenn/fenn/docs/ which doesn't exist, resulting in a 404.

This is because source_repository and source_directory in conf.py are set to the main fenn repo instead of the dev-docs repo.

Fix: Update html_theme_options in conf.py:

• source_repository → https://github.com/pyfenn/dev-docs
• source_directory → "" (empty, files are at repo root)