* Add footer extra links template

* [Docs] Update to mention extra links footer template

* Commit suggestion from @davidsvantesson

Co-Authored-By: David Svantesson <davidsvantesson@gmail.com>

* Move template placement to right side of footer

Co-authored-by: David Svantesson <davidsvantesson@gmail.com>
Co-authored-by: Lauris BH <lauris@nix.lv>

These templates add content to the top navbar
and to the repository page.
This way we do not have to copy and modify the whole
template, and re-modify it after upgrading Gitea if
it changes.

Signed-off-by: Alberto González Palomo <bugs@sentido-labs.com>