Fix settings.useMonospaceFontGlobal

When settings.useMonospaceFontGlobal is set to `true`, it sets the default
font to 'monospace'. This font seems to have been removed in
a5164dad43.

This commit sets the default font to "RobotoMono" which is a valid
option.

Tested in a Docker environment, setting `PAD_OPTIONS_USE_MONOSPACE_FONT`
to `true`

Signed-off-by: Xavier Mehrenberger <xavier.mehrenberger@gmail.com>

src/static/js/pad.js

@@ -338,7 +338,7 @@ const handshake = () => {
 
       // If the Monospacefont value is set to true then change it to monospace.
       if (settings.useMonospaceFontGlobal === true) {
-        pad.changeViewOption('padFontFamily', 'monospace');
+        pad.changeViewOption('padFontFamily', 'RobotoMono');
       }
       // if the globalUserName value is set we need to tell the server and
       // the client about the new authorname