add example for querying SHARP data and constructing a Map

[exitflynn]

PR Description

Adds an example gallery entry for querying SHARP data and then constructing a Map. Closes #6663.

[nabobalis]

I am not sure if the example runs, can you check that I didn't break it?

[wtbarnes]

A few minor changes. The RTD preview has not rendered yet either and I'd like to take a brief look at that before approving.

[wtbarnes]

Sorry, I did not catch several things on first review, namely that the example does not work in its current state.

[exitflynn]

i think there mustn't be anymore changes left to make now?

[nabobalis]

Have you checked if the example works and renders nicely on RTD?

[exitflynn]

i built the docs on my system using sphinx-build and there was indeed a minor problem. all fixed now, everything looks good to me!

[wtbarnes]

This still needs a changelog.

[nabobalis]

I will merge after I glance over the RTD version.

[nabobalis]

Thanks @exitflynn for the example

[exitflynn]

thank you so much for the reviews as well, Nabil and Will! 🤠