* Run screenshotter using Chrome 83 and Firefox 76
* Update screenshots
* Update NegativeSpace-chrome screenshot
The new screenshot is correct as per #1194.
* Update Units-chrome screenshot
The new screenshot is correct as per #732 and compared to Firefox.
* Update screenshots
This is almost like the align* environment, but it starts out in math mode,
so we don't have to worry about the fact that we have no real surrounding
text mode in KaTeX. This is the first step towards align* and align.