Remove py3.6, update dependencies, update docs

[ubaumann]

I wanted to share the document with a coworker and realised it is not up to date. I did some housekeeping like:

• removing Python 3.6
• adding Python 3.9 and 3.10 to the tests (like Nornir has)
• adding tasks.networking to the docs
• adding inventory.transform_functions to the docs
• update dependencies
• rebuild docs

[dbarrosop]

Awesome work, thx!