feat: add rendering for inline math

[nfejzic]

Rendering of math

This PR introduces parsing and rendering of Unimarkup math inlines.

Relevant decisions you made in this PR

An additional dependency mathemascii is introduced to parse and render the AsciiMath content.

The parsing is done together with rendering in the render_inline_math function. This is sub-optimal, we do not want parsing in rendering implementation. However, we will have to introduce a step (or multiple steps) between parsing and rendering for interpretation of logic, substitution etc. Parsing of math should happen after this resolving step, and before rendering.

What is now possible?

You can now use inline math in unimarkup, like this: $$sum_(i=0)^n i = (n(n+1))/2$$ which renders as .

NOTE: I used image embed here, because GitHub's inline math is broken right now: $\sum_{i=0}^{n} i = \frac{n(n+1)}{2}$.

Implementation of block rendering would be fairly easy (check out formalize for example, and live demo). The only part really missing is the parsing of math blocks. That can be done in a separate PR.

[mhatzl]

really nice work 👍
thanks for the integration :)

The resolve step and math block will come at a later point.
Therefore, I am merging this PR as is.