Make --timeout error message prettier

[simonw]

Following #47:

 % shot-scraper https://www.cnn.com/ -h 800 --timeout 5
Traceback (most recent call last):
  File "/Users/simon/.local/share/virtualenvs/shot-scraper-sQHOtKI2/bin/shot-scraper", line 33, in <module>
    sys.exit(load_entry_point('shot-scraper', 'console_scripts', 'shot-scraper')())
  File "/Users/simon/.local/share/virtualenvs/shot-scraper-sQHOtKI2/lib/python3.10/site-packages/click/core.py", line 1128, in __call__
    return self.main(*args, **kwargs)
  File "/Users/simon/.local/share/virtualenvs/shot-scraper-sQHOtKI2/lib/python3.10/site-packages/click/core.py", line 1053, in main
    rv = self.invoke(ctx)
  File "/Users/simon/.local/share/virtualenvs/shot-scraper-sQHOtKI2/lib/python3.10/site-packages/click/core.py", line 1659, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/Users/simon/.local/share/virtualenvs/shot-scraper-sQHOtKI2/lib/python3.10/site-packages/click/core.py", line 1395, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/Users/simon/.local/share/virtualenvs/shot-scraper-sQHOtKI2/lib/python3.10/site-packages/click/core.py", line 754, in invoke
    return __callback(*args, **kwargs)
  File "/Users/simon/Dropbox/Development/shot-scraper/shot_scraper/cli.py", line 190, in shot
    shot = take_shot(context, shot, use_existing_page=use_existing_page)
  File "/Users/simon/Dropbox/Development/shot-scraper/shot_scraper/cli.py", line 576, in take_shot
    page.screenshot(**screenshot_args)
  File "/Users/simon/.local/share/virtualenvs/shot-scraper-sQHOtKI2/lib/python3.10/site-packages/playwright/sync_api/_generated.py", line 7886, in screenshot
    self._sync(
  File "/Users/simon/.local/share/virtualenvs/shot-scraper-sQHOtKI2/lib/python3.10/site-packages/playwright/_impl/_sync_base.py", line 111, in _sync
    return task.result()
  File "/Users/simon/.local/share/virtualenvs/shot-scraper-sQHOtKI2/lib/python3.10/site-packages/playwright/_impl/_page.py", line 611, in screenshot
    encoded_binary = await self._channel.send("screenshot", params)
  File "/Users/simon/.local/share/virtualenvs/shot-scraper-sQHOtKI2/lib/python3.10/site-packages/playwright/_impl/_connection.py", line 39, in send
    return await self.inner_send(method, params, False)
  File "/Users/simon/.local/share/virtualenvs/shot-scraper-sQHOtKI2/lib/python3.10/site-packages/playwright/_impl/_connection.py", line 63, in inner_send
    result = next(iter(done)).result()
playwright._impl._api_types.TimeoutError: Timeout 5ms exceeded.

[simonw]

 % shot-scraper https://www.cnn.com/ -h 800 --timeout 5  
Error: Timeout 5ms exceeded.