[New] Default value (Argument assignment) is not recognized in Class statement

[Thirumalai-Shaktivel]

$ lpython --show-ast examples/expr2.py --tree --new-parser
syntax error: Token '=' is unexpected here
 --> examples/expr2.py:1:39
  |
1 | class _DTypeDict(_DTypeDictBase, total=False):
  |                                       ^