Add default issue template (MR 3980)

Previously this was set in the project settings, but according to the
GitLab documentation this can now be set using this file since GitLab
version 14.8. Keep it here to make sure it's version controlled as well.

.gitlab/issue_templates/Default.md

@@ -0,0 +1,46 @@
+<!--
+	Thank you for using postmarketOS! In order to speed up process of resolving your issue,
+	we would like you to fill in the following :
+-->
+### Describe your issue
+#### What's the expected behaviour?
+
+#### What's the current behaviour?
+
+#### How to reproduce your issue?
+
+### What device are you using?
+<!--
+	Leave name of your device in vendor-codename format.
+	If unsure, check name in the device package or leave full name of device
+	PinePhone: which revision exactly? See https://wiki.pine64.org/index.php/PinePhone#Hardware_revisions
+-->
+
+### On what postmarketOS version did you encounter the issue?
+<!--
+	Replace space inside `[ ]` with `x` to fill the checkbox
+-->
+* [ ] edge (`master` branch)
+* [ ] `v22.12`
+
+* [ ] I confirm that the issue still is present after running `sudo apk upgrade -a`
+
+### On what environment did you encounter the issue?
+#### Environments
+* [ ] Phosh
+* [ ] Plasma Mobile
+* [ ] Sxmo (Wayland/Sway) **Please post the output of `sxmo_version.sh`**
+* [ ] Other: **Please fill out**
+### How did you get postmarketOS image?
+* [ ] from https://images.postmarketos.org
+* [ ] I built it using pmbootstrap
+* [ ] It was preinstalled on my device
+### What's the build date of the image? (in yyyy-mm-dd format)
+<!--
+	Notes:
+		can be left empty if unsure
+		If you downloaded image from images.postmarketos.org, date will be in yyyymmdd format
+-->
+
+### Additional information
+<!-- logs, etc. -- make use <details> for long listings -->