[Feature Request] get_activities()

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Is your feature request related to a problem? Please describe.

`get_activities()` is not available in `Alpaca-py`

### Describe the solution you'd like.

Please add `get_activities()`
it was available in the old SDK `alpaca-trade-api `

### Describe an alternate solution.

If can't be added as a feature in the current `Alpaca-py`, then make this feature available in the website.
Create a menu in the website, to filter and export activities

### Anything else? (Additional Context)

I'm closing these issues now to avoid duplicate:
https://github.com/alpacahq/alpaca-py/issues/192
https://github.com/alpacahq/alpaca-trade-api-python/issues/800