Responded to @kasparsd:
There is a schemas.wp.org domain which redirects to the relevant version of the schema file in the Gutenberg repository https://github.com/WordPress/gutenberg/tree/trunk/schemas such as:
- https://schemas.wp.org/trunk/block.json
- https://schemas.wp.org/trunk/theme.json
- https://schemas.wp.org/trunk/wp-env.json
VS Code supports this out of the box https://code.visualstudio.com/docs/languages/json#_json-schemas-and-settings