docs: browserless.createContext() should be awaited in example

<img width="903" alt="Screenshot 2024-12-27 at 15 20 43" src="https://github.com/user-attachments/assets/89e39ee7-9086-4629-bb0d-99472674dd50" /> Should instead be: ```javascript // 👇 Added await const browserless = await browser.createContext({ retry: 2 }) ```