Schema matching is based on top-level apiVersion and kind only.
Multi-document YAML is supported. The extension scans documents separated by ---.
A single YAML file may resolve to multiple schemas.
Schema association happens at the file level because this is how vscode-yaml works.
Because association is file-level, a YAML file that contains multiple different document kinds may receive multiple schemas for the whole file, not one schema per individual document.
The current matcher is lightweight and line-based. It expects apiVersion: and kind: to appear as normal top-level scalar fields.
