GUACAMOLE-1760: Add documentation for VNC compression and quality par…

…ameters.

src/configuring-guacamole.md

@@ -544,6 +544,19 @@ available to work around such issues.
   parameter is optional. By default, lossy compression will be used when
   heuristics determine that it would likely outperform lossless compression.
 
+`compress-level`
+: Controls the level of compression requested of the VNC server when either
+  tight or zlib encoding is in use, on a scale of 0 to 9, with 0 being no
+  compression and 9 being the highest level of compression. Note that this
+  is negotiated with the server, and ultimately the decision on the amount
+  of compression that is done is up to the VNC server.
+
+`quality-level`
+: Sets the JPEG qualit level, on a scale of 0 to 9, when the tight encoding
+  is in use, with 0 being the lowest image quality (but likely improved
+  compression and speed) and 9 being the highest image quality but with
+  reduced compression and speed.
+
 #### VNC Repeater
 
 There exist VNC repeaters, such as UltraVNC Repeater, which act as