Add example gallery to the docs

[samaloney]

Describe the feature

Add example gallery and a simple example maybe based on the waves or swaves.

Proposed solution

Should be able to essentially copy the configuration from sunpy docs and adapt as needed.

[hayesla]

@Amityush-lgtm if you also want to have a look at this too :)

[Amityush-lgtm]

Sure, I'll take a look at it