Feature request

In line with the requirement for generic objects, arrays and general type specification in level 6, it would be nice to have a rule which reports generic callable or Closure usage without specifying an expected signature in the PHPDoc.

ex. this should report an error about the prototype not being specified: https://phpstan.org/r/029b8b4c-5cd2-4d1b-85b0-f1544837dd79