✨ Show warnings if keys dont have description

[hofp37]

• README update

Resolves #5

[pavelsvagr]

1. This also applies to nested config keys. Usually, only the first-level fields are used since they can be set as env vars, but I don’t think we want to monitor what’s happening in nested fields if someone decides to use them. A comment on the first-level fields should be enough, right?

{
  "DB": { // This gets warning
     "host": "asdasd", // This get warning as well
     "port": "asad" // This get warning as well
  }
}

2. Be careful, that this is also valid json:

{
            "DB"           :          false
}

[pavelsvagr]

Invalid env file here can break the code in my opinion (missing {} and first line is the matching pattern).

"EXTENSION FAIL": "nothing"

Documentation says that document.lineAt() expects non-negative int. Could you secure this case?