add action to quick toggle space visibility
This adds an entry to the xmlgui action list, so user can add it to Kate or KWrite to quickly toggle whitespace visibility.
Somewhat related:
cc @aacid
By the way, what does the "show non-printable spaces" option do? I originally wanted something similar to Notepad++'s "Show all characters", which will also show characters like CR, LF but the "show non-printable spaces" action doesn't seem to do that.
Edited by Gary Wang