feature: Support PEP 846 when it's accepted #492

Is your feature request related to a problem? Please describe.

PEP 846 makes it so that docstrings below type alias assignments (type T = ...) are now attached to the type AST node, as doc attribute, and the literal string after the assignment is removed from the AST.

Describe the solution you'd like

We should support this new AST shape. This only affects Python 3.16+.

Describe alternatives you've considered

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Additional context

https://discuss.python.org/t/pep-846-docstrings-for-type-aliases/109116