This adds the ability to redirect URLs with `#` fragments. This is
useful when section headers get renamed or moved to other pages.
This works both for deleted pages and existing pages.
The implementation requires the use of JavaScript in order to manipulate
the location. (Ideally this would be handled on the server side.)
This also makes it so that deleted page redirects preserve the fragment
ID. Previously if you had a deleted page redirect, and the user went to
something like `page.html#foo`, it would redirect to `bar.html` without
the fragment. I think preserving the fragment is probably a better
behavior. If the new page doesn't have the fragment ID, then no harm is
really done. This is technically an open redirect, but I don't think
that there is too much danger with preserving a fragment ID?
Nim is a systems programming language (included in the highlight.js
`system` group), and we're quite happily using `mdBook` in several of
our documentation projects starting with our [style
guide](https://status-im.github.io/nim-style-guide/).
While we can maintain our own highlight.js, including `Nim` in the
default distribution would allow us to promote more mdBook usage in the
Nim community at the cost of a ~2kb increase in the `highlight.js` size.
Allows for special styles to call them out since they're different than
normal text and different than code. They can make use of styles they
inherit for font style and weight.
Notes on changes:
- Added new CSS variables for reused elements
- The font-* rules are separate for each aspect so that they can inherit
bold/italic/etc
Closes https://github.com/rust-lang/mdBook/issues/1813
