Document version scheme (#245)

* Document version scheme #121

* Document how to tag

Author: raboof

CONTRIBUTING.md

@@ -64,7 +64,11 @@ install Xephyr and run the scripts
 
 ## Releasing and versioning
 
-Currently under discussion at https://github.com/raboof/notion/issues/121
+We don't publish binaries, that is up to the distributions.
+
+Releasing is simply a matter of setting the relevant git tag
+(by revising and publishing the [draft](https://github.com/raboof/notion/releases/)).
+Whether to update the minor or patch level is decided case-by-case.
 
 ## Getting in touch