[Bug]:README fix for market docs URL

[desavera]

Is there an existing issue for this?

• [X] I have searched the existing issues

Current Behavior

As simple as pointing to an updated URL : https://docs.alpaca.markets/ for the market doc link.

Expected Behavior

The URL for the market doc changed to : https://docs.alpaca.markets/

SDK Version I encountered this issue in

LATEST

Steps To Reproduce

just open the README and the link for the market doc is a 404

Filled out the Steps to Reproduce section?

• [X] I have entered valid steps to reproduce my issue or have attached a minimally reproducible case in code that shows my issue happening; and understand that without this my issue will be flagged as invalid and closed after 30 days.

Anything else?

Keep on ROCKING !!!

[hiohiohio]

@desavera Thank you for the report! Fixed.