Document use of virtual env

[FabienDanieau]

Example of use of conda, virtenv, etc

See @RemiFabre 's comment pollen-robotics/python-coding-guidelines#4

Also it would be nice to add a small section on the usage of virtual environments. I use this:
https://virtualenvwrapper.readthedocs.io/en/latest/
No need to write a whole guide on this, a 1 liner with this link (for example) seems enough.

[FabienDanieau]

Interesting article about conda and venv : https://whiteboxml.com/blog/the-definitive-guide-to-python-virtual-environments-with-conda
Conda is preferred over venv because it provides real isolated env.

I would recommend this for newbies in the documentation

[RemiFabre]

+1
Plus conda seems more ROS friendly