Example demo and end-to-end test

[willscott]

• Create a simple but demonstrative go-ipld-prime schema
• Create a car file matching that schema
• Create an example graphql server over that schema and data
• Create a test to exercise expected queries of the generated code

[felixboehm]

As there is only an outdated hint to an non existing example folder in the readme, this would help a lot.

[willscott]

For sure!

for now you can look at a couple of the places that use it it to see:

• you hook into this against a schema. this is from when we would deal with schemas using codegen rather than bindnode, but a bindnode-loaded schema will work the same. Here's an example

This then generates schema.go. The part that isn't generated and which uses that schema would in this case is server.go