Jack compiler now supports underscores in identifier

jack_compiler/src/tokenizer.rs

@@ -359,7 +359,7 @@ fn parse_keyword_or_identifier(chars: &Vec<char>, tokens: &mut Vec<Token>, index
     token_string.push(chars[index]);
     index += 1;
 
-    while chars[index].is_alphanumeric() {
+    while chars[index].is_alphanumeric() || chars[index] == '_' {
         token_string.push(chars[index]);
         index += 1;
     }