Leverage MyST Cross-Referencing in Contribution Guides

[jukent]

There are two versions of the Cookbook Contribution Guide, it would be nice if we leveraged MyST's cross-referencing capabilities so that a reader is quickly directed to the relevant longer text explanation of those steps in the long guide from the shorter guide.

Similarly the all pythia guide, portal, and foundations guides all reference each other.

[brian-rose]

Getting a few working examples within our own content for how to do this, and showing why it's a good idea, would be helpful for new cookbook developers.