Extend parser to support int as hexadecimal and numeric underscore.

We only allow numeric underscore for decimal numbers as I am not sure how we can define it for non-decimal numbers?

crates/aiken-lang/Cargo.toml

@@ -25,6 +25,7 @@ strum = "0.24.1"
 thiserror = "1.0.39"
 vec1 = "1.10.1"
 uplc = { path = '../uplc', version = "1.0.7-alpha" }
+num-bigint = "0.4.3"
 
 [target.'cfg(not(target_family="wasm"))'.dependencies]
 chumsky = "0.9.2"