misc: add bug report template for Gitlab issues

This adds a "Bug" template that users can select when creating new
issues on Gitlab.

Change-Id: I8b7f17be03a8437b13970c58a7519759f8d94cf9

.gitlab/issue_templates/Bug.md

+Bug report form
+---------------
+
+## OS
+
+<!-- e.g. Debian, Ubuntu, etc. -->
+
+## Jami daemon version:
+
+<!-- type `/usr/lib/ring/dring -h` into your terminal -->
+
+## Jami GNOME client version:
+
+<!-- type `jami-gnome -v` into your terminal -->
+
+## Where did you get Jami?
+
+<!-- (add an x in between the square brackets to select an option) -->
+
+- [x] My OS package manager (e.g. apt, yum, pacman)
+- [ ] I downloaded it from jami.net
+- [ ] I built it from source using the make-ring.py script
+- [ ] I built it from source manually or other (please explain):
+
+## Steps to reproduce bug
+
+<!-- The better your scenario is, the better we will be able to help
+you. Please try to describe only one bug here. Open multiple issues
+for multiple bugs -->
+
+Steps:
+
+1.
+
+2.
+
+## What you expect to happen:
+
+## What happens instead:
+
+## Logs
+
+<!-- run
+
+journalctl --since "24h ago" | grep dring
+
+in your terminal -->
+
+## Additional information
+
+<!-- Screenshots/videos/logs/etc
+
+Include a backtrace here if the program is crashing. -->
+
+For more information about getting logs, see
+https://git.jami.net/savoirfairelinux/ring-project/wikis/tutorials/Bug-report-guide#logs.