add validate method

index.ts

@@ -10,7 +10,14 @@ export function load_theme(name: string) {
 		return null;
 	}
 
-	return structuredClone(require(`./themes/${name}/theme.json`));
+	const theme = require(`./themes/${name}/theme.json`);
+	validate_theme(theme);
+
+	return structuredClone(theme);
+}
+
+export function validate_theme(theme: unknown) : asserts theme is ColorTheme {
+	// todo: validate
 }
 
 export type ColorThemeLabel