feature request: check if script references are valid

[moritzjacobs]

For example:

"scripts": {
    "test": "run-s test:unit lint",
    "test:unit": "jest",
    "test:lint": "eslint ./src"
}

should throw a scriptlint error because the script was renamed from lint to test:lint but the user forgot to change the reference in the test script as well.

This should be smart enough to go for npm run <foo>, yarn <foo>, and all variants of npm-run-all/run-p etc.