add direction observer and improve sizeobserver tests

packages/testing-browser/src/Select.ts

@@ -16,7 +16,7 @@ export const generateSelectCallback = (targetElm: HTMLElement | null) => (event:
     const selectOptions = getSelectOptions(target);
 
     if (targetElm) {
-      targetElm.classList.remove(...selectOptions);
+      selectOptions.forEach((clazz) => targetElm.classList.remove(clazz));
       targetElm.classList.add(selectedOption);
     }
   }

packages/testing-browser/src/Timeout.ts

@@ -0,0 +1 @@
+export const timeout = (ms: number) => new Promise((resolve) => setTimeout(resolve, ms));