Remove missed trace of beta ribbon
Added a link to the GitHub repository.

There is no GitHub link in the page, so a link was added for better discovery.
Made some room for another footer link.

Reduced the padding of the footer links, in preparation for the new GitHub link.
Updated the GitHub link.

The GitHub link referred to the default branch, so it was changed to the development branch, by request of Jacob Rossi.
Revert "Updated the GitHub link."

This reverts commit 87b23bb89a0bc83ace8780902f3c5c5daf180baf.