Readme and the example json

[markkelnar]

This contains some fixes to the readme, queries, links, images, etc. Nothing too dramatic. I did remove showing the screenshot of GraphiQL of each query as

• some image content didn't match the example and I didn't take a new screenshot.
• Seemed like duplication to have code block of the graphql query and the return json above each screenshot. The code block seems super useful for copy/pasting the example query.

Chose to add the example acf fields as json instead of zip file so we can see it and source control it in a way that seems more transparent of what is actually in there.

Solve: #199

[jasonbahl]

@markkelnar I like the changes here! This JSON file will be helpful for folks looking to get up to speed, and will serve as a reference for when we make changes to things like how Field Groups can be assigned to the GraphQL Schema.

We can point to diffs of this registration file to show how things worked before, and how they work after, etc. 🙌

At first I was unsure about all the images being removed, but reading the docs without them does feel better! Good change!