Compiler TypeScript Support

[sinclairzx81]

This PR is a subsequent update on #469 to add return type annotations on generated functions.

const T = Type.Object({
  x: Type.Number(),
  y: Type.Number(),
  z: Type.Number(),
})

const C = TypeCompiler.Code(T, [], { language: 'typescript' })

// produces

return function check(value: any): boolean {
  return (
    (typeof value === 'object' && value !== null && !Array.isArray(value)) &&
    (typeof value.x === 'number' && Number.isFinite(value.x)) &&
    (typeof value.y === 'number' && Number.isFinite(value.y)) &&
    (typeof value.z === 'number' && Number.isFinite(value.z))
 )
}