Keyboard shortcut to invert colors

I'm using this with cool-retro-term and it's great! The only problem is that pages with light backgrounds can be a little blinding.

I hacked a version that hard codes logic to invert all the RGB values and it works perfectly for making bright pages dark and readable. But then pages in night mode are too bright!

I think the ideal for me would be a keyboard shortcut like ctrl-i that toggles the color inversion. That way as I'm navigating through pages I can choose the most readable version.

Very cool project! It's awesome to have a usable browser from the terminal.