Create LatexMathsComponent

Generate Component class in `/addon` directory, to allow the consuming
application to import and modify the component class.

Create wrapper component in `/app` directory, so manually importing the
component is not necessary.

Include KaTeX library in `/vendor/katex`

Add acceptance tests

Add unit tests

Observe input expression and 'display' property:
  - set output style
  - store rendered expression value
  - render LaTeX with KaTeX