Update virtual-device.md

On my system there was no file called .venv\Scripts\activate.bat. Instead it was .venv\bin\Activate and "Activate" was the bat file that worked so added those additional instructions under "1. Activating the virtual environment".

1-getting-started/lessons/1-introduction-to-iot/virtual-device.md

@@ -60,6 +60,10 @@ Configure a Python virtual environment and install the pip packages for CounterF
         ```cmd
         .venv\Scripts\activate.bat
         ```
+     OR    
+     ```cmd
+        .venv\bin\Activate
+        ```
 
     * On macOS or Linux, run: