Write developer notes for improved documentation of key parts of the library

Created by: RasmusOrsoe

Is your feature request related to a problem? Please describe. Larger libraries tend to have "developer notes". They tend to include explanation of key parts of the library in a article-sized format. I think it might be worthwhile for us to consider if we should do the same for 1.0.0.

Additional context See https://pytorch.org/docs/stable/index.html for examples on developer notes.