gitignore: Add Python venv folder

[nexton-winjeel]

I often use a Python virtual environment to ensure I'm using the correct versions of Python modules. This PR adds the default venv folder to the .gitignore.

[Ryanf55]

Hey there, Ardupilot already creates a virtual environment in ~/venv_ardupilot, which is the default. Have you tried using that one?

[nexton-winjeel]

Hi @Ryanf55, my issue is that I've got a couple of different forks, so I want to be able to set a venv per repo, not per machine.

[khancyr]

Environments

.env
.venv
env/
venv/
ENV/
env.bak/
venv.bak/

from https://github.com/github/gitignore/blob/4488915eec0b3a45b5c63ead28f286819c0917de/Python.gitignore#L125

Not sure why we would need to check subdirectory ?

[nexton-winjeel]

Not sure why we would need to check subdirectory ?

Do you mean why did I add **/venv/ rather than venv/? Because I wanted to be able to create a venv on a per-vehicle basis, and I thought I needed the ** to achieve that.

Updated.

[nexton-winjeel]

@khancyr: I've updated to include all the different Python environment folders.