Create a custom.css for small theme CSS additions

[metamoof]

Problem

Today I came across a bug when upgrading from mdbook 0.5.3 to 0.5.4 - that I had an image that was included doubly all of a sudden.

This had to do with the new zoomable image feature, which required new parts in general.css

I've added some small classes for some headings in my general.css, and so I had a custom file. Merging the two is an additional step that requires a bit of finesse.

Proposed Solution

I suggest an empty custom.css file be included in the standard theme, maybe with a comment explaining that this is for small enhancements.

Including an edited version of this file in theme/css would allow my custom heading styles and so on to live on without needing to merge the general.css file every time there is an update to mdbook.

Notes

No response

[metamoof]

Additionally, this can be used by extensions such as mdbook-epub without needing to duplicate information in files.

[metamoof]

Hmm, this is actually a documentation issue.

You should mention the output.html.additional-css option in the theme section of the docs.