Explain how to start the container after building it

[hamishwillee]

This update the container guide a little to tidy the English. I also took the opportunity to add information on how the built file can then be used.
I was testing this on Windows and it works there too - so even though it isn't really the use case, I added a note explaining that it can be done.

@mrpollo The docker image builds QGC fine, but it appears to build a release version. How can I tell it I want to build a debug version. Often the main reason for me to want to build this is to create a mocklink - which can only be done on debug I believe.

We probably want this configurable.

Further, is there any information about how to package this into an image? Would be great for deployment if that was explained?

Further, do you know if Airmap and Video are automatically set up by this?