Move to TypeScript

[slifty]

Task

Description

TypeScript will do a lot for this project.

(1) We already have a forced concept of abstract classes, types, and interfaces in the ecosystem. This could be done more robustly (and with fewer lint rule overrides) with TypeScript.
(2) This will allow TypeScript projects to use TV Kitchen.
(3) We could remove runtime type checks in the countertop (speeding up the project).

Converting Base to TypeScript is the right first step.

It may turn out that some of the base packages become obsolete / certain things like interfaces should be moved to the countertop directly, but I'll leave that decision to the time of implementation

[slifty]

Instead of updating this repo directly I'd actually like to deprecate it and move the code over to countertop. See tvkitchen/countertop#154)