Add equations parsing

[lmmx]

Developer docs page: Equation

An Equation may contain EquationFunction, EquationSymbol, and Text elements.

• Very basic, smaller than MathJax's vocabulary, doesn't even support bold typefaces
• Unclear what the output format is. Symbols not given as any sort of enum on developer site, nor in TypeScript docs
  • if not exposed to API (like e.g. kix comment anchors weren't) then waste of time developing for it
• There's a symbol conversion table to LaTeX here

	\alpha
	\beta
	\gamma
	\delta
	\epsilon
	\varepsilon
	\zeta
	\eta
	\theta
	\vartheta
	\iota
	\kappa
	\lambda
	\mu
	\nu
	\xi
	\pi
	\varpi
	\rho
	\varrho
	\sigma
	\varsigma
	\tau
	\upsilon
	\phi
	\varphi
	\chi
	\psi
	\omega
	\Gamma
	\Delta
	\Theta
	\Lambda
	\Xi
	\Pi
	\Sigma
	\Upsilon
	\Phi
	\Psi
	\Omega

	\times
	\div
	\cdot
	\pm
	\mp
	\ast
	\star
	\circ
	\bullet
	\oplus
	\ominus
	\oslash
	\otimes
	\odot
	\dagger
	\ddagger
	\vee
	\wedge
	\cap
	\cup
	\aleph
	\Re
	\Im
	\top
	\bot
	\infty
	\partial
	\forall
	\exists
	\neg
	\angle
	\triangle
	\diamond

	\leq
	\geq
	\prec
	\succ
	\preceq
	\succeq
	\ll
	\gg
	\equiv
	\sim
	\simeq
	\asymp
	\approx
	\ne
	\subset
	\supset
	\subseteq
	\supseteq
	\in
	\ni
	\notin

	\frac
	\sum
	\sqrt
	\rootof
	\subsuperscript
	\subscript
	\superscript
	\abs
	\overline
	\widehat
	\tilde
	\bigcap
	\bigcup
	\prod
	\coprod
	\int
	\oint

	\leftarrow
	\rightarrow
	\leftrightarrow
	\Leftarrow
	\Rightarrow
	\Leftrightarrow
	\uparrow
	\downarrow
	\updownarrow
	\Uparrow
	\Downarrow
	\Updownarrow