* Update to rougify 3.26.1 styling
* Adapt background overwrite by removing default background color
and only adding explicit overwrites for syntax error
(error stylings appear for example in json-excerpts –
see HACKING.md – and are therefore hidden by our css)
h1 font weight is defined to be 100 but no font-face
definition for weight 100 is included.
The browser will use the nearest available font-weight
instead. As that is 400, we do specify it explicitly now.
Those were added in b41a3f66c9 without
an explicit license, so they are under the default license. Some files
already got a header previously, so this only touches the remaining.
The same should be done for docs/_data/extra_pages.json, but it's json, and
json doesn't allow comments.
