Add function constructor for literals

[BobVarioa]

Title. Parsing the arguments is somewhat hacky, whenever/if we pull in acorn or perhaps only after #34, we should parse these correctly.
This is also vunerable to this type of "attack" (below), but currently I don't really see a better way to do it?

$ ./porf
> Function('a) { return 1 }; void function (', 'return 2')() // should throw
1

But definitely a correctness bug, albeit minor.

(+0.04 Test262 tho 🎉)