Add pagecolor support
Add pagecolor support

Ignore pagecolor support as done for clientside MathJax in
https://gerrit.wikimedia.org/r/#/c/61256/1/modules/MathJax/extensions/TeX/texvc.js

Bug: T107578
physikerwelt/MathJax,wikimedia/MathJax,GerHobbelt/MathJax,GerHobbelt/MathJax