GitHub icon and link to GitHub for book #7
Description
To explicitly mark the book as open-source it would be nice to have a GitHub icon at the top of the page(s) that links to the book GitHub, as is very common in open-source projects (example below from Adidoks):
In addition, on the landing page (https://learntheoreticalphysics.com/) we should do the same, with a navbar that includes a GitHub icon to link to our GitHub.