Update Python package instructions for Windows

Author: WillSams

README.md

@@ -89,8 +89,8 @@ Execute the following in your terminal:
 
 ```bash
 python -m venv venv
-source venv/bin/activate
-pip install --upgrade pip 
+source venv/bin/activate  # for Windows, source venv/Scripts/activate
+python -m pip install --upgrade pip 
 pip install -r requirements.txt
 ```