add more typedefs

[sritchie]

#25 Introduced infrastructure for typings. Remaining TODOs:

To-do:

• add typings for mathBox options
• finish manual typings for types.js
• add more tests to types.spec.ts. Since that test file is written in typescript, if its tests pass, we can be confident in my manual typings.

[sritchie]

@ChristopherChudzicki we might be done with this, yeah?

[ChristopherChudzicki]

The types for types.js are not really done. A bunch are still any: https://github.com/unconed/mathbox/blob/master/src/primitives/types/types_typed.ts#L207-L222

I think this will be "done" when those are all finished. I'm pretty sure I'll add scale soon, and will look more closely at the others when I do that.