[Feature] Add support for Schwab

[arsaboo]

Can we add support for Schwab API - https://github.com/alexgolec/schwab-py

[edtechre]

Thank you for the suggestion @arsaboo, I will look into adding this.

[edtechre]

Hi @arsaboo,

On further consideration, I won't be adding support for a Schwab data source. This is because I want to keep dependencies to a minimum, where YF and Alpaca are available primarily as examples to get people started.

Instead, you can simply query to the Schwab API and then use the returned DataFrame as a data source. See https://www.pybroker.com/en/latest/notebooks/7.%20Creating%20a%20Custom%20Data%20Source.html#Using-a-Pandas-DataFrame.