Add Binary LogicalType

As a developer, I wish I could use Woodwork to categorize columns that contain only one of two values with a logical type of `Binary`. This would be useful in setting up machine learning classification problems as users would clearly know that the target column with a `Binary` logical type contains only two values and they should structure the problem as a binary classification and not a multi-class classification.

The `Binary` logical type should have a dtype of `category` as it should work with multiple data types including strings, integers and doubles. Missing values should be allowed. This should not include boolean values of `True` and `False` as those should be recognized as a `Boolean` or `BooleanNullable` logical type. `Binary` should be a child type of `Categorical`.

#### Code Example

```python
import pandas as pd
import woodwork as ww
from woodwork.logical_types import Binary

df = pd.DataFrame({"binary_col": ["yes", "no", "no", "yes"]})
df.ww.init()

assert isinstance(df.ww.logical_types["binary_col"], Binary)

```