As a user, I can use inline or block math syntax to write mathematical formulae in my annotations

[nickstenning]

• [x] I can create an annotation including content such as "$$f(x) = \int_{-\infty}^\infty \hat f(\xi)\,e^{2 \pi i \xi x} \,d\xi$$" and see it rendered as math in its own block.
• [x] I can create an annotation including content such as "(f(x) = \int_{-\infty}^\infty \hat f(\xi)\,e^{2 \pi i \xi x} \,d\xi)" and see it rendered as math inline.

[nickstenning]

Implemented in hypothesis/h#1451.