Show output when all tests pass

[SiddharthShyniben]

There should be some encouraging output like ✅  All test pass when all tests pass. Not only it is encouraging, I also think that it looks like something is broken if it is not included. Example:

$ npm run lint 

> app@1.0.0 lint
> xo
$ # Prompt comes out of nowhere, something looks broken...

I ran the command 2-3 times and modified the code for sometime until I realized that there were no problems...

[sindresorhus]

The Unix convention is silent on success and verbose on error. I prefer that too.

You can use xo && echo Success if you need confirmation that it worked.