Refactor to TypeScript

[blakeembrey]

Alternative to #59. I prefer to author in TypeScript and skip the infrastructure around testing types independently. Uses the same scripts as path-to-regexp for automatic formatting and testing.

This PR doesn't break backward compatibility in the API (but does in node.js version support). It minimally changes the code and tests to add types and test using vitest.

I plan to add benchmarks (using the built-in vitest framework) and optimize the code paths (similar to the work done for cookie) in further PRs. I think there's at least a 50% bump available, and that may require minor API changes (e.g. avoid assigning to an object).

[bjohansebas]

Is the namespace necessary here, or is it enough to just export it?

[blakeembrey]

You can't export anything extra because I left it in CommonJS format with export =.

[blakeembrey]

I tried not to refactor too much in this PR and left that for the perf one, this one is more of a direct port with types added.

[bjohansebas]

Basically, what I found is that we should add #66 and keep the changes we made in #57 to remain strict with the spec. So any changes after that which were merged into master shouldn't be included in this new version, except for tests. Other than that, this was just my first pass through the spec after a long time. I'll keep an eye on it once you've done the rebase.