Math: Add \Q, \H and \AA texvc commands to MathJax

\Q and \H doublestruck versions of Q and H
\AA used for Angstrom symbol

Bug: 35186
Change-Id: I20ac8af2253835c20431585d9caebe4066606879
Merge "Math: Add \Q, \H and \AA texvc commands to MathJax"