readme fixes

README.md

@@ -43,11 +43,11 @@ I would like to maintain a list of online amateur radio receivers on <a href="ht
 
 ## Usage tips
 
-You can zoom the waterfall display by the mouse wheel.
+You can zoom the waterfall display by the mouse wheel. You can also drag the waterfall to pan across it.
 
 The filter envelope can be dragged at its ends and moved around to set the passband.
 
-However, if you hold the shift key, you can drag the center line (BFO) or the whole passband (PBS).
+However, if you hold down the shift key, you can drag the center line (BFO) or the whole passband (PBS).
 
 ## Configuration tips