Support type annotations via typing.Generic

[honorabel]

It would be great if both the range value type and mapped value type could be annotated with type annotations, e.g.:

@dataclass
class Foo:
  a: int
  b: str

tree = IntervalTree[int, Foo]()

tree[2, 5] = Foo(123, 'test')

# linter should raise type error:
tree[1.4, 2.3] = Foo(123, 'test')

# linter should raise type error:
tree[2, 5] = 'invalid value type'

[Lubba-64]

Here are some experimental type stubs:
https://github.com/Lubba-64/intervaltree-stubs

[iainelder]

@Lubba-64 how do we use them?

[Lubba-64]

I created these type stubs while in a clone of the original repo. I do not recall how or if I set it up for production, I ended up with a custom solution to replace this library anyways since my use case was different.