Updating the readme with a walkthrough

[adamakhtar]

Hi @codereading/readers im updating the readme with a walkthrough of the codebase plus a few other nice to have bits.

So far it's mostly outlines and rough english. If you see something you want to add or edit, go ahead and ill merge it in. Ill add contributors names to the top as well.

If I/we can make something useful for others I'm thinking of creating a jekyl blog for the organization where we can post such walkthroughs.

Ill create another topic for the walkthrough as well.