* Server-side syntax hilighting for all code

This PR does a few things:

* Remove all traces of highlight.js
* Use chroma library to provide fast syntax hilighting directly on the server
* Provide syntax hilighting for diffs
* Re-style both unified and split diffs views
* Add custom syntax hilighting styling for both regular and arc-green

Fixes #7729
Fixes #10157
Fixes #11825
Fixes #7728
Fixes #3872
Fixes #3682

And perhaps gets closer to #9553

* fix line marker

* fix repo search

* Fix single line select

* properly load settings

* npm uninstall highlight.js

* review suggestion

* code review

* forgot to call function

* fix test

* Apply suggestions from code review

suggestions from @silverwind thanks

Co-authored-by: silverwind <me@silverwind.io>

* code review

* copy/paste error

* Use const for highlight size limit

* Update web_src/less/_repository.less

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

* update size limit to 1MB and other styling tweaks

* fix highlighting for certain diff sections

* fix test

* add worker back as suggested

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

change status icon for merged PR to git-merge

Signed-off-by: a1012112796 <1012112796@qq.com>

Co-authored-by: guillep2k <18600385+guillep2k@users.noreply.github.com>

Move langauge detection to separate module to be more reusable

Add option to disable vendored file exclusion from file search

Allways show all language stats for search

The choice regarding which forms should or should not trigger a warning
is subjective. I tried to be consistent and not warn about forms that:
 - run an action, rather than edit data: search, send an email.
 - delete data: a warning about losing data would be confusing

Note that forms on sign-in pages were already ignored (using a selector,
rather than an explicit class on the form element).

Fixes #3698.

Signed-off-by: Jonas Franz <info@jonasfranz.de>

Indexed search of repository contents (for default branch only)