`Style` is unhashable

[kdeldycke]

Bug description

Style caches its click.style() keyword arguments on first call, in a field declared without compare=False and repr=False:

cloup/src/cloup/styling.py

Line 174 in bfb76dc

_style_kwargs: Optional[Dict[str, Any]] = dc.field(init=False, default=None)

To Reproduce

>>> from cloup import Style
>>> a, b = Style(fg="red"), Style(fg="red")
>>> a == b, hash(a) == hash(b)
(True, True)
>>> a("hello")
'\x1b[31mhello\x1b[0m'
>>> a == b
False
>>> hash(a)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<string>", line 32, in __hash__
TypeError: unhashable type: 'dict'