Allow for header customization #182
Description
This related to a discussion here
Is your feature request related to a problem? Please describe.
I'd love to use jupyter book for my textbooks. i have 3 currently on our learning portal. the problem is that because we have multiple books and a portal that is SEO optimized, we want to maintain visual branding of all of our content. This means that ideally we'd like to have the ability to add a header to the book with links back to our main site and to customize the css /colors potentially to better match our existing theme. The site currently is being redesigned btw.
As i'm considering this a footer element would be nice to have too - at CU we have to acknowedge certain things in the footer.
Describe the solution you'd like
I'd like a simple way to adding a header with HTML to all book html pages.
This will likely mean we also need to be able to add stuff to the header (above the <body> tag in the <head> section - which might include css and also js.
Describe alternatives you've considered
i've considered creating our own theme but that seems like a lot of work to add a header and css to a page! i'd also have to learn a lot of new things to customize sphinx.
Additional context
have a look at our website and you will see on the home page links to three textbooks. in the site they retain the site skin. they are not separate websites.
thank you for considering this!