Minor 0.0.1a4

[ryanmphill]

This pull request updates how favicon links are managed in the static site generator. The favicon is no longer hardcoded in the HTML builder; instead, it is now included via the head_extra configuration, allowing for more flexible and customizable head content. Related tests and configuration files have been updated to reflect this change.

Configuration and Metadata Handling:

• Added the default favicon link (<link rel='icon' type='image/x-icon' href='/favicon.ico'>) to the head_extra list in config.json, making favicon management part of the site configuration instead of hardcoded in the HTML builder.
• Updated test configuration to include the favicon link in the head_extra array, ensuring test coverage for the new approach.

HTML Builder and Rendering:

• Removed the favicon_link parameter and its usage from the HTMLRootLayoutBuilder.get_doc_head method, so favicons (and other head elements) are now injected via head_extra.

Testing Updates:

• Updated tests in test_data_loader.py to expect the favicon link as part of the head_extra metadata, adjusting assertions and indices accordingly.
• Removed assertions expecting the favicon link to be hardcoded in the HTML output, and adjusted test names and logic to match the new configuration-driven approach.

Miscellaneous:

• Bumped the project version from 0.0.1a3 to 0.0.1a4 in pyproject.toml.