Allowlist/blocklist for operator types as well

[danthedeckie]

as noted in:

>>> import simpleeval
>>> class Foo:
...     def __add__(self, other):
...         raise Exception('alas!')
...
>>> simpleeval.simple_eval('foo + 21', names={"foo": Foo()})
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/daniel/src/simpleeval/simpleeval.py", line 768, in simple_eval
    return s.eval(expr)
           ^^^^^^^^^^^^
  File "/Users/daniel/src/simpleeval/simpleeval.py", line 433, in eval
    return self._eval(previously_parsed or self.parse(expr))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/daniel/src/simpleeval/simpleeval.py", line 445, in _eval
    return handler(node)
           ^^^^^^^^^^^^^
  File "/Users/daniel/src/simpleeval/simpleeval.py", line 448, in _eval_expr
    return self._eval(node.value)
           ^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/daniel/src/simpleeval/simpleeval.py", line 445, in _eval
    return handler(node)
           ^^^^^^^^^^^^^
  File "/Users/daniel/src/simpleeval/simpleeval.py", line 502, in _eval_binop
    return operator(self._eval(node.left), self._eval(node.right))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/daniel/src/simpleeval/simpleeval.py", line 272, in safe_add
    return a + b
           ~~^~~
  File "<stdin>", line 3, in __add__
Exception: alas!

so should we have a way to only run the various __add__ etc operators on classes that have been explicitly allowed to?