ask the Funkwhale version on bug report

.gitlab/issue_templates/Bug.md

@@ -34,6 +34,12 @@ Describe the expected behaviour.
 
 ## Context
 
+<!--
+The version of your instance can be found on the footer : Source code (x.y)
+-->
+
+**Funkwhale version(s) affected**: x.y
+
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 If relevant, share additional context here like: