misc(logger): add warn level

[doteric]

Summary

There is a missing log level between error and info which is simply warn to show just errors and warnings and nothing else. Very small and simple change required to add some better experience.

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[connorjclark]

Some failing tests to address FYI

[doteric]

@connorjclark
https://github.com/GoogleChrome/chrome-launcher/blob/main/src/chrome-launcher.ts#L17
https://github.com/GoogleChrome/chrome-launcher/blob/main/src/chrome-launcher.ts#L38

That's pretty odd typing a little bit. Any suggestions what should be done about it?
lighthouse-logger needs to be updated if we want to change it in chrome-launcher otherwise it wouldn't make sense...
IMO. the typing is broken.

[connorjclark]

If you can send a PR to update chrome-launcher in the same way, we can update all at once.

Another option is to add // @ts-expect-error explaniation in the place where typescript is erroring in the lighthouse repo.

[doteric]

@connorjclark
GoogleChrome/chrome-launcher#295
But I think it might be worth removing that type from chrome-launcher and infer from lighthouse-logger in the future 🤔

[connorjclark]

Thanks @doteric!