Add documentation about PiCamera2 and virtual enviroments

[VgerTest]

Great examples, but it took me a while to run them because of the "no module called libcamera" issue till I found this:
https://forums.raspberrypi.com/viewtopic.php?t=361758

python3 -m venv --system-site-packages env

Maybe it's worth adding this to readme.

Thanks

[automaticdai]

Thank you so much. I will add this into the README.md.

The install script actually bypasses this by skipping creating a venv if an RPi device is detected.