Rewrite client with Typescript

[rmorshea]

Current Situation

Currently IDOM's client is implemented in Vanilla JS. This makes it easy to develop and contribute to, but the code-base is growing in complexity, and without unit tests, there's some risk that it will become difficult to maintain.

Proposed Actions

Rewrite the client using typescript. Type annotations seem to be coming to browser Javascript engines soon so, like with Python, typed Javascript is likely to grow in popularity. Type annotations are not a replacement for unit tests, but they will help. It will also be a form of documentation that can be referred to by new contributors and users.

[Archmonger]

Should we switch to TS, or simply wait for JavaScript to support type hints?

[rmorshea]

I'm not really sure how it's going to pan out, but from my understanding, they're not re-inventing the wheel - the syntax is identical to TS so if we wrote in TS it should work as-is in the future.