Update Contributing docs and add tox as test optional-dependency

[hdub-tech]

DISCLAIMER

Long time ansible-lint user, first time contributor, and also first time working
directly with a Python project. I'm trying to do things "right" but might have
missed the mark. Feedback welcome so I can get better!

Description

Problem: The contributing docs are a little lacking on how to get up and go and,
while they encourage running tox tests, tox is not included as a test dependency.

Solution: This PR

1. Improves documentation aimed at first time Contributors
2. Adds tox as an optional test dependency
3. Adds some common venv paths to .gitignore
4. Cleans up some output for tox list
5. Cleans up some output in tox run -e hook

Testing

• tox installed with pip install -e .[test]

  BEFORE:
  

  AFTER:
  
  

• git ignores .venv

  BEFORE:
  

  AFTER:
  

• tox list no longer has a dangling and

  BEFORE:
  

  AFTER:
  

• Add --initial-branch=main to test-hooks.sh to get rid of big warning.

  BEFORE:
  

  AFTER:
  

• tox run -e lint,pkg,docs,py

  

Outstanding questions / TODOs

If someone has the answers for these, I'm willing to update this PR to include it.

1. If there was a test that should be updated / added for this PR, please point me to the desired
   location and I will do the needful.
2. Should the DCO file be removed since the --signoff requirement was removed in Clean up the DCO & --signoff mentions from CONTRIBUTING.md #719?
3. I didn't update the docs to mention the need to have npm installed for the tox run -e schemas.
   I see the workflows are using setup-node and a cache-dependency-path but I didn't see a quick
   way to utilize this in a fresh local install. Thoughts?

[ssbarnea]

@hdub-tech Thanks for the PR. I am not yet sure if adding tox itself to test deps is a good idea or not but I will let it in. Time will tell.