Add reference to the repo to schemastore

[joellabes]

Context:

https://github.com/SchemaStore/schemastore/blob/master/CONTRIBUTING.md

Schemata can be hosted directly on schemastore, or they can be stored in a separate repository with schemastore providing a reference to the raw file.

Upload to schemastore directly

Pros:

• Allows refs to work across files (only possible on local files)
• We can upload positive and negative test files to validate the validator, without building our own

Keep files in this repo and just set up a reference in schemastore

Pros:

• Single source of truth
• We have control over PR flow and can rapidly iterate if needed
• Versioning is tidier - we can point old versions to a tagged commit instead of having an entire different copy of the file (compare for example agripparc-1.2.json, agripparc-1.3.json, agripparc-1.4.json)

[joellabes]

I think that we should keep the files here and just hotlink to the repo:

• The files are pretty static, so a bit of repetition in the refs doesn't seem like the end of the world
• Nice versioning and ease of releasing changes feels more important to me