extensions/json-language-features/client/src/jsonClient.ts/getSchemaId
function getSchemaId(schema: JSONSchemaSettings, folderUri?: Uri): string | undefined {
	let url = schema.url;
	if (!url) {
		if (schema.schema) {
			url = schema.schema.id || `vscode://schemas/custom/${encodeURIComponent(hash(schema.schema).toString(16))}`;
		}
	} else if (folderUri && (url[0] === '.' || url[0] === '/')) {
		url = joinPath(folderUri, url).toString();
	}
	return url;
}