Add enum provider

[NazarioJL]

What does this change

Adds an enum provider to allow users to generate values based on enums.

Usage:

from enum import Enum

from faker import Faker


class Color(Enum):
    RED = 1
    GREEN = 2
    BLUE = 3


fake = Faker()
fake.enum(Color)
# One of [Color.RED, Color.GREEN, Color.BLUE]

[fcurella]

Thank you! Looks really good!

[fcurella]

Could you run make lint to fix the formatting issues?

[NazarioJL]

@fcurella need me to do anything else?

[fcurella]

No, thank you. I'll take it form here and fix the mypy issues :)