Fix lexer throwing errors when parsing a too large tuple index.

crates/aiken-lang/src/tests/parser.rs

@@ -1864,6 +1864,15 @@ fn parse_tuple2() {
     );
 }
 
+#[test]
+fn large_integer_constants() {
+    let code = indoc! {r#"
+      pub const my_big_int = 999999999999999999999999
+    "#};
+
+    assert_definitions(code, vec![])
+}
+
 #[test]
 fn plain_bytearray_literals() {
     let code = indoc! {r#"