Currently when opening the main framework pages there is no introduction
to the framework. Instead we only see a whole lot of modules and the
`gem_version` and `version` methods.

By including the READMEs using the `:include:` directive each frameworks
has a nice introduction.
For markdown READMEs we need to add the :markup: directive.

[ci-skip]

Co-authored-by: zzak <zzakscott@gmail.com>