add async support

[tonyfettes]

No description provided.

[peter-jerry-ye-code-review]

‼️ This code review is generated by a bot. Please verify the content before trusting it.

Here are three observations from the provided git diff output:

1. Inconsistent Handling of apply_operator in apply_expression:

   • In the apply_expression rule, the apply_operator is now used instead of directly including ! or question_operator. However, in the test files (asi.txt, expression.txt, and test.txt), the apply_operator is sometimes used, but in other cases, the question_operator is still directly referenced. This inconsistency might lead to confusion or errors in parsing. Ensure that all instances are updated to use apply_operator consistently.

2. Potential Missing apply_operator in test.txt:

   • In test.txt, there is a line with (apply_operator) but no associated value or operator. This might be a typo or an incomplete implementation. Verify if this is intentional or if an operator (like ! or !!) should be specified here.

3. New async Keyword Integration:

   • The async keyword has been added to function definitions and lambda expressions. While this is a valid addition, ensure that all related test cases and documentation are updated to reflect this change. Specifically, check if the async keyword is correctly handled in all contexts, such as in function_definition, anonymous_lambda_expression, and function_type.

These observations highlight areas where further review or testing might be necessary to ensure consistency and correctness in the grammar and parsing logic.