[gnome-music/wip/jfelder/readme-improvements: 3/3] README: Add a debugging paragraph

[Jean Felder <jfelder src gnome org>]

commit 5d33670f535dc1cf31fe1ab2bcc8d22d46438dc8
Author: Jean Felder <jfelder src gnome org>
Date:   Thu May 14 22:40:18 2020 +0200

    README: Add a debugging paragraph

 README.md | 8 ++++++++
 1 file changed, 8 insertions(+)
---
diff --git a/README.md b/README.md
index 217dc8da..7af1e256 100644
--- a/README.md
+++ b/README.md
@@ -33,6 +33,14 @@ You can also install Music system-wide by running:
 $ ninja install
 ```
 
+## Debugging
+
+GNOME Music uses [GLib logging facilities](https://developer.gnome.org/glib/stable/glib-running.html) to 
print debug messages. It can be activated by setting the `G_MESSAGES_DEBUG` environment variable:
+
+```sh
+G_MESSAGES_DEBUG=org.gnome.Music gnome-music
+```
+
 ## Coding style
 
 GNOME Music is written in Python and adheres to the coding style described in the python style guide 
[PEP-8](https://www.python.org/dev/peps/pep-0008/).