Reimplement Index assignments

[Vurv78]

iirc in the past I allowed for any expression to precede variable assignment so stuff like _G["foo"] = 55 "worked". Currently this isn't the case so the readme example actually doesn't parse.

Need to actually have this work by allowing for indexing by checking for an indexing operation for every identifier since stuff like this is possible.

_G["bar"], _G.foo = 55, 40
print(bar, foo) -- 55, 40

[Vurv78]

Hopefully resolved by 231a6b8