Switch to side-by-side view

--- a/doc/upmpdcli.txt
+++ b/doc/upmpdcli.txt
@@ -61,6 +61,7 @@
 page. <<upmpdcli.presentationnote,See note>>|||presentationhtml
 |Run a command (or shell script) when playback is about to begin.|||onstart
 |Run a command (or shell script) when playback is about to end.|||onstop
+|Run a command (or shell script) when volume is changed.|||onvolumechange
 |===========================    
 
 [[upmpdcli.iconpathnote]]