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 #132 (comment). Having some of these graphics included in the docs would be awesome!

Originally posted by @andersy005 in #132 (comment)

[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.