Create a design doc for this project

[maaverik]

We have one for the frontend repo, which details the tools used and guidelines on what components should go where.

In this repo's case, I feel that there aren't going to be many tools used, but a brief description of the different components, intended folder structure, and overall flow of data would be useful not just for us to be on the same page, but also for more experienced go programmers to guide us and contribute more easily.

Once we have a decent design doc ready, we could also set up individual GitHub issues or maybe a checklist of things to do, because there aren't a lot of sync ups between contributors except through PRs right now. Discussing the design of components in issues worked well for the frontend repo, it helped new contributors get up to speed from looking at the discussions and allowed them a space to ask questions.

The design doc just needs to give a high-level overview. For more up-to-date and specific information, let's add inline documentation that can be rendered with godoc. This gives a quick cheatsheet on how to create inline documentation in go.

More discussions here: https://github.com/SimplQ/simplQ-golang/pull/7/files#issuecomment-999458450