Add Compile-Time Type-Checking using tl

tl is a static type checker for Lua: https://github.com/teal-language/tl/blob/master/docs/tutorial.md (like TS for JS). It would be great to have optional type annotations in moon+ so that moon+ compiles to tl, which then checks and compiles to Lua.

Two issues come to mind:

• Figuring out the type annotation syntax in moon+
• Changing the compiler to keep those annotations. Fortunately, there shouldn't be an issue even for the moonscript-specific class types, because they can be represented by records: https://github.com/teal-language/tl/blob/master/docs/tutorial.md#records

Or, the tl type checker portion could be ported to the moon+ compiler. The majority of code in the tl compiler (https://github.com/teal-language/tl/blob/master/tl.tl) is the actual parser and AST traversal, which could be replaced by the existing parser in moon+.

Start by reading the issue's linked Teal tutorial and the referenced tl.tl compiler source. Investigate how YueScript currently parses and compiles syntax, then resolve the proposed annotation syntax and whether annotations should be preserved for Teal or type checking should be ported. Done means a defined approach is implemented and validated for MoonScript-specific class types.