Simplest quite mode implementation for plugin

[imanbee]

Hi @adamduncan!
First of all, thank you for your plugin! Works great :)
Quiet mode is a need for me, so I'm proposing simplest flag to have an ability to suppress warnings / errors in console.
I know it can be improved as option to choose between warnings and errors or even all output, so please let me know what is your vision regarding this option.

[adamduncan]

Thanks @imanbee 👍

Will put some thought into the API here. quietMode: true certainly does the job, as intended with #15.

I wonder if there's some preexisting logLevel Node convention that might be preferable? 🤔

[imanbee]

Usually Node.js uses one of these options to set logLevel : trace/debug/info/warn/error.
If we want to use same convention, that "fallback" locales output should be visible only for logLevel: "warn" and not for `logLevel: "error"'. So I think only these two options might be available at the moment, however in the future you can always extend for any "lower" level of logging

[imanbee]

And we can possibly use https://www.npmjs.com/package/loglevel package to control current logLevel and automatically disable logging which has lower level