Return "Invert Colours" as a shortcut key in Mountain Lion

Thanks to @bunnyhero for this tip. I'm generally really happy with Mountain Lion, but Apple decided to turn off the CMD+ALT+CRTL+8 shortcut that inverted the colour scheme. This is a feature I use on a regular basis, as I prefer to look at a black background with white text when I'm writing.

Turns out, it's actually pretty easy to turn it back on. Simply find the Keyboard menu in system preferences, click on "keyboard shortcuts", and click the box that says "Invert colours." The keyboard shortcut works again. Phew.