Add TypeScript Test File

[jonobr1]

Describe the solution you'd like
Two.js needs a test.ts file that attempts to use all the features available in Two.js in the ways they are intended to use. This is like the tests written in JavaScript, but for TypeScript. This will greatly improve the stability and accessibility for TypeScript developers by making the types.d.ts file accurately reflect the capabilities of Two.js.

Additional context
See Definitely Typed's approach for reference: https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/types/two.js/two.js-tests.ts