Add #include statement

[vurvdev]

Add another statement in the parser that accepts #include "path". (Might also need to add a new keyword to tokenizer)
See https://github.com/wiremod/wire/wiki/Expression-2#include-directive for more info on what include is.

( It is basically just #include from languages like C++, except it is not through the preprocessor but it is turned into a function that runs in another scope.. yeah it's weird.. )

If you really want to go above and beyond you can also implement it in the lua transpiler side as just require(string).