Typesafe regexp patterns

[timvandam]

This PR introduces a regexp pattern parser, which improves the type safety of regexp literals.

For example:

const UserId = type("/^user_[^_]$/#UserId") // Type<Brand<`user_${string}`, "UserId">, {}>
const UserAccountId = type("/^user_account_[^_]$/#UserAccountId") // Type<Brand<`user_account_${string}`, "UserAccountId">, {}>
const PostId = type("/^post_[^_]$/#PostId") // Type<Brand<`post_${string}`, "PostId">, {}>

Regexp patterns can be used in many places, so downstream type safety also improves as a result of this PR. For instance, the following test case:

const t = type({
	"[/^f/]": {
		a: "1"
	},
	"[/f$/]": { b: "1" },
	foof: { c: "1" }
})

const a = t.get("foo")
// Previously:
attest<{ a: 1 } | { b: 1 }>(a.infer)
// Now:
attest<{ a: 1 }>(a.infer)

const b = t.get("oof")
// Previously:
attest<{ a: 1 } | { b: 1 }>(b.infer)
// Now:
attest<{ b: 1 }>(b.infer)

The following tasks still need to be wrapped up:

• Fix test cases
• Fix error handling (either<a,b> does not seem efficient - use something like StaticState?)
• Fix excessively deep type instantiation (introduced after merging with upstream + adding error handling - hopefully error handling is all that needs to change here)
• Add negative test cases to assert the correct errors are raised