Allow f strings

[TheBlueMoonEclipse]

Add f strings so we can make code easier like so:

(mind you the 'print' action is the macro) rule 'pizza': print('hello {}'}.format('world') ^ hard

rule 'pizza': print(f'hello {'world'}') ^ easy

[CactusPuppy]

Zezombye has commented on Discord that it would be difficult to tokenize format strings. As of right now I lack the bandwidth to tackle this issue, but I agree it would be very nice to have.

[nathan130200]

Maybe using some libraries like Antlr (a bit slow) or GNU Bison (faster), but writing grammars/parsers are painful 💀💀