We'll have to fix several problems:

• Implement support for SVG with references: #211
• Improve support for ex units as they are used to control math equation sizes and currently they are sometimes too small.
• Add support for rem units as they are used to set the padding: #264
• Implement support for var() custom variables as they control the line-height.

Test pages:

• https://en.wikipedia.org/wiki/Maxwell%27s_equations
• https://en.wikipedia.org/wiki/Quantum_entanglement
• https://en.wikipedia.org/wiki/Wave_function
• https://en.wikipedia.org/wiki/Dirac_delta_function
• https://en.wikipedia.org/wiki/Fourier_transform
• https://mathworld.wolfram.com/FourierTransform.html
• https://en.wikisource.org/wiki/On_Einstein%27s_Theory_of_gravitation