Add the -rotate parameter

Usage.md

@@ -42,7 +42,7 @@ Usage: moonlight [action] (options) [host]
         -unsupported            Try streaming if GFE version or options are unsupported
         -quitappafter           Send quit app request to remote after quitting session
         -viewonly               Disable all input processing (view-only mode)
-
+        -rotate [0|90|180|270]  Rotate the video output with the specified number of degrees, clockwise (default 0)
  WM options (SDL and X11 only)
 
         -windowed               Display screen in a window