Please support static typing

#### My Pain

I'm developing my applications in the VS Code editor. Furthermore I use pylint and mypy to help me create code of high quality. And google style docstring for documentation.

Param unfortunately does not work that well with that.

I've tried something like that.

```python
class Scatter2dWithSelectionComponent(param.Parameterized):
"""The Scatter2dWithSelectionComponent enables a user to

- provide a DataFrame of data

Parameters
----------
data : pd.DataFrame
A dataframe of data to be shown and selected
"""
data: pd.DataFrame = param.DataFrame(precedence=0.1)
```

But

- VS Code cannot provide tab completion for `instance.data.` or help text on hover of `instance.data`.
- Pylint complains for example that `E1101: Instance of 'DataFrame' has no 'iloc' member (no-member)` if I have a line like `instance.data.iloc`.

#### Solution

Support static type checking and enable all the help you can get in modern editors.