Type check event handler functions

[rmorshea]

We should check that the given value is at least callable and raise a type error otherwise: https://github.com/idom-team/idom/blob/92e60b1d5f0057d359a9e12beb8a5de6e9d9b12a/src/idom/core/events.py#L174

[rmorshea]

This has been resolved in the 0.33 release