Instructions don't mention installing python dependencies

[CraigSiemens]

When building pico-blink for the first time, it produces the following error.

ModuleNotFoundError: No module named 'macholib'

After looking through the project I found the requirements.txt file and ran the following to fix the issue.

pip3 install -r ../Tools/requirements.txt

[rauhul]

Would you be interested in PR a documentation fix for this?

[mredig]

I actually just updated the docs myself with this and one or two more documentation clarifications. Is there a more formal process like the larger Swift project, or should I just open a PR?

[rauhul]

Just open a PR :)