Add small delay before screenshot is taken

Author: darrenburns

src/textual/app.py

@@ -641,6 +641,7 @@ async def press_keys() -> None:
                             await asyncio.sleep(0.02)
 
                     await app._animator.wait_for_idle()
+                    await asyncio.sleep(0.05)
 
                     if screenshot:
                         self._screenshot = self.export_screenshot(