* 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
These commands set their arguments in a given TeX math class. Use
the existing "op" type for \mathop (to support \limits); introduce
a new "mclass" type for the other classes.
Fixes#482. Tests borrowed from #485 (cbreeden).