Sphinx Math Support

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In Sphinx, when there are two newlines in an equation block, these are intercepted and treated as a aligned (e.g. here) equations or split environment. This makes it very easy for users to create multiline equations.

Resources:

• Sphinx docs: https://sphinx-rtd-trial.readthedocs.io/en/latest/ext/math.html#directive-math
• Feat: Sphinx-like Math rendering jupyterlab-myst#53
• Requesting issue Alignment with mystjs jupyterlab-myst#57 (comment)

This is requested in support of the jupyterlab plugin to be as close as possible to the sphinx output.