* Don't manually replace whitespace during render

For historical reasons Gitea manually alters the urlPrefix and replaces
a whitespace with a +. This Works for URLs, but we're also passing
urlPrefix to git calls and adding the + is breaking the tree path.

Goldmark will automatically convert a white space to the proper %20, so
we should leave the string as is which lets us pass it to git unmodified
and then let Goldmark fix it.

Also fixed separate bug in URLJoin I noticed while testing where it will
silently discard sections of a path that have # in them (possibly
others). We should just escape it first.

Fixes 10156

* Escape elems as well

* Revert "Escape elems as well"

This reverts commit 8bf49596fe.

* restart ci

* remove changes to URLJoin

* restart ci

Co-authored-by: techknowlogick <matti@mdranta.net>

Co-authored-by: Lauris BH <lauris@nix.lv>

* Move to goldmark

Markdown rendering moved from blackfriday to the goldmark.

Multiple subtle changes required to the goldmark extensions to keep
current rendering and defaults.

Can go further with goldmark linkify and have this work within markdown
rendering making the link processor unnecessary.

Need to think about how to go about allowing extensions - at present it
seems that these would be hard to do without recompilation.

* linter fixes

Co-authored-by: Lauris BH <lauris@nix.lv>