RFE: render MD/RST documents in tree view

[Juuso Lapinlampi]

source-filter is good enough? I don't want cgit to become a GitLab-ish
platform with all this featuritis.

Do one thing and do it well; leave Markdown rendering to a seperate
program. Nobody can really even agree to how Markdown and its quirks
should be rendered, so we have tens of variants. CommonMark is not
stable yet.

(I'd actually wish cgit had a better config structure with less
options, or something like OpenBSD pf does.)

Please.