Docs explaining how to view query plans

[andygrove]

Which issue does this PR close?

Closes #.

Rationale for this change

Start showing off the nice functionality that we have.

What changes are included in this PR?

New section on query plans.

Are there any user-facing changes?

[andygrove]

@MrPowers @jdye64 fyi

[MrPowers]

This is so awesome! Well written.

In the future, might be cool to add a section on real-world use cases for this functionality. I'd stress that this is really hard to build from scratch, so many libraries are using the DataFusion query planning capabilities. We could also add a list of the libraries using this functionality. Perhaps we could highlight dask-sql as an example of a success story?

I think the PR is fine as-is and is a great addition to the documentation!

[andygrove]

I think the PR is fine as-is and is a great addition to the documentation!

Thanks. I'll merge this and follow up (likely next weekend) to address your suggestions. The next step is to explain how to inspect the individual operators and expressions (there are Python wrappers for them) and how to transpile to other query engines.

[jdye64]

Late to the party but this is great @andygrove thanks!