When rendering Asciidoc documents this merge request enables the diplay of
admonition blocks using font icons. This improves the looks of Asciidoc redered
files.
This uses the font-awesome fonts already present in Gitlab so no large
dependencies are required for this to work.
- Apply the RelativeLinkFilter filter to other formats, e.g.,
reStructuredText so links from the Files view or the Project view work
- Remove the AsciidocPipeline pipeline
Fixes#3533.
