[php-langspec][Issue #247] - Support changes in php 8.0 syntax?

You can view the Issue on github:
https://github.com/php/php-langspec/issues/247

Opened By: TysonAndre
Issue Description:
The following changes may matter for the language specification in PHP 8.0 - feel free to split out separate tickets

https://wiki.php.net/rfc/named_params
https://wiki.php.net/rfc/namespaced_names_as_token
https://wiki.php.net/rfc/nullsafe_operator
https://wiki.php.net/rfc/match_expression_v2
https://wiki.php.net/rfc/non-capturing_catches
Trailing commas in parameters/closure use
https://wiki.php.net/rfc/union_types_v2
https://wiki.php.net/rfc/static_return_type
https://wiki.php.net/rfc/mixed_type_v2

Additionally, the php 8.0 attributes syntax is still being voted on