Add support for the COSMIC desktop environment

This depends on https://gitlab.alpinelinux.org/alpine/aports/-/merge_requests/80719

Also depends on !6265 (merged)

.gitlab/issue_templates/Default.md

@@ -34,6 +34,7 @@
 
 ### On what environment did you encounter the issue?
 #### Environments
+* [ ] COSMIC
 * [ ] GNOME Shell on Mobile
 * [ ] Phosh
 * [ ] Plasma Mobile