* Add Matrix webhook

Signed-off-by: Till Faelligen <tfaelligen@gmail.com>

* Add template and related translations for Matrix hook

Signed-off-by: Till Faelligen <tfaelligen@gmail.com>

* Add actual webhook routes and form

Signed-off-by: Till Faelligen <tfaelligen@gmail.com>

* Add missing file

Signed-off-by: Till Faelligen <tfaelligen@gmail.com>

* Update modules/webhook/matrix_test.go

* Use stricter regex to replace URLs

Signed-off-by: Till Faelligen <tfaelligen@gmail.com>

* Escape url and text

Signed-off-by: Till Faelligen <tfaelligen@gmail.com>

* Remove unnecessary whitespace

* Fix copy and paste mistake

Co-Authored-By: Tulir Asokan <tulir@maunium.net>

* Fix indention inconsistency

* Use Authorization header instead of url parameter

* Add raw commit information to webhook

Co-authored-by: Lauris BH <lauris@nix.lv>
Co-authored-by: Tulir Asokan <tulir@maunium.net>