add mpv controls

README.org

@@ -61,6 +61,15 @@
        strm e*phants         # Play files whose path matches the wildcard 'e*phants'
    #+end_src
 
+   The usual [[https://mpv.io/manual/master/#interactive-control][mpv controls]] are available while playback.
+   Here is a subset:
+   
+   - =LEFT= and =RIGHT= :: Seek backward/forward 5 seconds.
+   - =UP= and =DOWN= :: Seek backward/forward 1 minute.
+   - =p= and =SPACE= :: Pause (pressing again unpauses).
+   - =<= and =>= :: Go backward/forward in the playlist.
+   - =q= :: Stop playing and quit.
+
 ** Configuration
 
    The scripts expects a configuration file with the following content: