Update docker documentation

[burtonrj]

Improve docker documentation to explain how to start the CytoPy image with a persistent volume and connect to a MongoDB server.

[JANHMS]

Just a quick note here. I had some small problems bringing up the container:

I needed to include some PATHS for file sharing within the docker desktop app.

[burtonrj]

Thank you for posting this and sorry about the lack of correspondence on issues. I'm currently finishing a research post and writing up my PhD thesis, so CytoPy has been a little neglected.

I have a new version (branch v3.0) in the pipeline with a tonne of new features and improvements to the original design. I'll be addressing install issues and docker with this release. At the moment I can't say for certain when that will be but hopefully later this year.