Add type annotations to the Luau variant of module

[Dekkonot]

Luau has a type system which is used for both intellisense and in some cases native codegen instructions. This PR adds type annotations.

This omits adding return-type annotations to expandBuffer. This is because this function actually can't really be represented by Luau's type type at the moment -- I believe this is a bug with Luau, but I will check with the maintainers. Regardless though, it's internal facing only so I think it's fine to leave without type annotations at the moment.

[RiskoZS]

I can see Luau having a hard time with expandBuffer as that function's return signature is effectively something like (nil, string) | (buffer, number) and Luau simply has no way to annotate something like that (sounds more like a limitation of the type system than a bug to me). However, for consistency's sake, I would prefer to not keep the function's return value unannotated. Even Luau complains about it in strict mode.

Annotating the return type as (buffer?, any) seems to appease the linter and is probably good enough; could you please amend the PR to include that?

[RiskoZS]

It also looks like Luau needs a bit of help on line 71 with determining that acceleration is non-nil

[RiskoZS]

It also looks like Luau needs a bit of help on line 71 with determining that acceleration is non-nil

[RiskoZS]

Annotating the return type as (buffer?, any) seems to appease the linter and is probably good enough