Move API reference to gi-docgen
GTK-Doc is falling into disrepair, and has various problems:
- redundant C parsing compared to the introspection data
- complicated set up, with multiple files required to generate the documentation
- custom Markdown implementation
- custom HTML generator
- DocBook → HTML roundtripping, with slow xsltproc transformation process
- outdated, non-responsive HTML style
The gi-docgen tool aims to solve these issues, by using only the introspection data to build the declaration and symbols tree, as well as extracting their documentation. Additionally, it transforms Markdown into HTML directly, and uses templates similar to static website generators that make it easy to restructure the HTML and style.