Migrate to TypeScript

[francisfuzz]

What would this project look like if the source and tests were written in TypeScript, the distribution were written in JavaScript, and some examples were included to show usage?

[francisfuzz]

For motivation, I do some pretty aggressive type and length checking here:

str-gen/index.js

Lines 19 to 30 in e411321

	// Return early if any of these conditions are true.
	if (
	// Type checks
	!is('Number', length) ||
	!is('Array', charset) ||
	// Length checks
	length <= 0 ||
	length > MAX_STRING_LENGTH ||
	charset.length === 0 ||
	charset.length > MAX_ARRAY_LENGTH) {
	return result
	}

I'd be keen to define that up front in the function definition if at all possible. Something that also comes to mind is ensuring that the build process is updated, along with the backing tests and examples, while retaining the original design -- I don't the behavior would constitute a breaking change, but the internals would certainly be changed as a part of this migration.

[francisfuzz]

Opened #13 as an extension of the way we implement max lengths within this function.