Document dependencies for platforms

[scarrazza]

Recently when installing qibolab with zh extras for qw5_platinum there are still missing packages such as pyvisa and qcodes. We should document this.

[alecandido]

I moved this here, since we need to do this for each and every platform.

And add this requirement to some documentation, such that it will be checked and added for future platforms as well.

[alecandido]

My proposal would be to add a README.md file in each platform.

This could be a good place to describe other platform features as well, but we can standardize a section with the platform requirements (e.g. Installation or Dependencies).
For all standard platforms, even a single command would be sufficient, something like:

pip install qibolab[qm, twpa]