Add more graphics to the docs

[maxrjones]

As suggestion in Anderson's review of #132, some of the diagrams included in the issues/PR discussions would be useful to add to the documentation to explain how the batch generator works.

I really like the graphics in https://github.com/xarray-contrib/xbatcher/pull/132#issue-1473258637. Having some of these graphics included in the docs would be awesome!

Originally posted by @andersy005 in https://github.com/xarray-contrib/xbatcher/issues/132#issuecomment-1360500014

[cmdupuis3]

I had an idea for a graphic that basically shows how input_overlap can be used to create halos. I'll let you know when that's done

[0xSaksham]

Is anybody working on this? If not, I can take it up.