feature: add EAS metadata store config schema

[byCedric]

Linked issue

Add IntelliSense for store.config.json (EAS Metadata) to the plugin.

Additional context

This uses the concept of contributes.jsonValidation and pulls the schema directly from the repository, without additional modifications or manual download.

This might become problematic if we have multiple versions. But even then, we could combine them in a single JSON schema and conditionally apply them based on the configVersion constant.

[byCedric]

Note, we shouldn't link this to the actual development branch. New features could be rolling out unexpectedly to users, even when they aren't published.

Proposed solution

Create a dedicated branch on this repo where we keep the manifests. We could pre-modify the XDL schema, and pull the EAS Metadata schema from the latest eas-cli :). That way, we can roll out updates as soon as they are available.

• Proposed branch name would be schemas
• CI could help with keeping these schemas up to date
• CI scripts should not live in that branch, just on main
• Commit only when there are changes to the schema, and only commit it to schemas branch

This approach also fixes #83, and avoids issues like #87 in the future

[byCedric]

Superseded