Link to "Mystery Person" SVG.

README.md

@@ -57,7 +57,8 @@ specified fallback in the URL and in the environment variable.
 
 If you want to support "Mystery persons" (mp/mm) as default avatars, place a
 file named `mp` in the avatar dir. You can use the [default libravatar mystery
-person](https://seccdn.libravatar.org/mm/512.png), for example.
+person](https://seccdn.libravatar.org/mm/512.png)
+([SVG](https://git.linux-kernel.at/oliver/ivatar/raw/master/ivatar/static/img/mm.svg)), for example.
 
 Test your setup on https://www.libravatar.org/tools/check/.