Documentation: add examples for adding job dependencies

[adwk67]

Our docs and demos contain a fair amount of information about how to add python- and jvm-dependencies, but this would be easier to understand (and to refer to) if there were a short list of examples as to how to do this, a bit like has been done for resources here, and to augment what we already have here.

Issue checklist

• There exists a documentation page dedicated to showing the different ways to add python libraries and java jars and packages: added to a custom image built on one of our product images (as we do here), added as spec.deps.packages, added as python requirements using spec.deps.requirements etc.etc.
• Notes are added to indicate which spark versions support these methods.