feat(frontend): allow selecting multiple original languages

src/types/custom.d.ts

@@ -22,3 +22,11 @@ declare module '*.png' {
   const content: any;
   export default content;
 }
+
+declare module '*.css' {
+  interface IClassNames {
+    [className: string]: string;
+  }
+  const classNames: IClassNames;
+  export = classNames;
+}