Transition to Quarto built-in solution for GitHub "Edit this page" links (when available)

[ravicodelabs]

Currently, Quarto couples its table of contents feature (toc) with its GitHub "Edit this page" feature. Since we don't always use a toc, there isn't a straightforward way for us to have the "Edit this page" link on each page.

As a workaround, we created a post-render script render_scripts/github_link_insertion.ts to insert the GitHub links. Once the Quarto project adds the appropriate functionality in, we can transition to a Quarto built-in solution rather than maintain the render script approach.

As @mine-cetinkaya-rundel explained in issue #35, the Quarto project has an issue open for this here: quarto-dev/quarto-cli#2142.

[ravicodelabs]

Moved this to the Quarto-related issue tracker: #115