docs: Elaborate on issue reporting

We currently just link to the issue tracker without providing
any further guidance.

Improve on that by pointing to the appropriate handbook chapter,
point out extensions as a possible source of issues, and direct
users towards discourse/matrix for support/discussions.

Based on a similar section in gnome-shell's README.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell-extensions/-/merge_requests/352>

README.md

@@ -23,8 +23,6 @@ branch.
 
 Please refer to the [schedule] to see when a new version will be released.
 
-Bugs should be reported to the GNOME [bug tracking system][bug-tracker].
-
 [schedule]: https://release.gnome.org/calendar
 
 ## Extensions
@@ -109,6 +107,27 @@ project.
 
 [alternatetab-post]: https://blogs.gnome.org/fmuellner/2018/10/11/the-future-of-alternatetab-and-why-you-need-not-worry/
 
+## Reporting bugs
+
+Bugs should be reported to the [issue tracking system][bug-tracker].
+
+The [GNOME handbook][bug-handbook] has useful information for creating
+effective issue reports.
+
+Please note that the issue tracker is meant to be used for
+actionable issues only.
+
+For support questions, feedback on changes or general discussions,
+you can use:
+
+ - the [#gnome-shell matrix room][matrix-room]
+ - the `Desktop` category or `extensions` and `shell` tags on [GNOME Discourse][discourse]
+
+[bug-tracker]: https://gitlab.gnome.org/GNOME/gnome-shell-extensions/issues
+[bug-handbook]: https://handbook.gnome.org/issues/reporting.html
+[matrix-room]: https://matrix.to/#/#gnome-shell:gnome.org
+[discourse]: https://discourse.gnome.org
+
 ## License
 
 GNOME Shell Extensions are distributed under the terms of the GNU General
@@ -116,5 +135,4 @@ Public License, version 2 or later. See the [COPYING file][license] for details.
 Individual extensions may be licensed under different terms, see each source
 file for details.
 
-[bug-tracker]: https://gitlab.gnome.org/GNOME/gnome-shell-extensions/issues
 [license]: COPYING