docs: Add Mopidy-Local-SQLite extension

docs/ext/backends.rst

@@ -90,6 +90,19 @@ Mopidy-Local
 Bundled with Mopidy. See :ref:`ext-local`.
 
 
+Mopidy-Local-SQLite
+===================
+
+https://github.com/tkem/mopidy-local-sqlite
+
+Extension which plugs into Mopidy-Local to use an SQLite database to keep
+track of your local media. This extension lets you browse your music collection
+by album, artist, composer and performer, and provides full-text search
+capabilities based on SQLite's FTS modules. It also notices updates via
+``mopidy local scan`` while Mopidy is running, so you can scan your media
+library periodically from a cron job, for example.
+
+
 Mopidy-Podcast
 ==============