Devtools: add the option to fail silently if port wasn't found

[marcofugaro]

Hey, currently in our project, we use the devtools like this:

export const overmind = createOvermind(config, {
  devtools: process.env.NODE_ENV === 'development',
});

And we use the VSCode extension to access the devtools.

However sometimes, we might not be working on the state, and therefore we don't have the devtools open.

This results in the classic error log polluting the console:

Would be useful if we could have an option to tell the devtools to "fail silently" if no port was found.

[grandevel]

See PR already here - #533

[marcofugaro]

Thanks! Would like for this to be configurable as well, however with an option for "don't show anything at all"