add $schema and $id to all json schema

[k-yle]

This will prevent bugs like #172 by showing JSON schema errors in your IDE

[tordans]

For reference https://code.visualstudio.com/docs/languages/json#_json-schemas-and-settings

[tordans]

I can confirm this improves working in VS Code.

I don't know a lot about those properties but Copilot is happy when I asked about it…

Yes, the $schema and $id properties in your field.json file are correct.

The $schema property specifies the version of the JSON Schema standard that this schema adheres to. In this case, it is using the draft-07 version of the JSON Schema standard.
The $id property provides a unique identifier for the schema, which is useful for referencing it in other schemas or documents.
Using the draft-07 version of the JSON Schema standard is a good choice as it is widely supported and provides a robust set of features for defining and validating JSON data structures.