github: Add reference to incus bug report

Signed-off-by: Benjamin Somers <benjamin.somers@imt-atlantique.fr>

Author: bensmrs

.github/ISSUE_TEMPLATE/bug-reports.yml

@@ -1,5 +1,5 @@
 name: Bug report
-description: File a bug report.
+description: File a bug report. You can also use the command incus bug report.
 type: bug
 body:
 - type: checkboxes