no-outside-dependencies

Don't import from DefinitelyTyped/node_modules.

Bad:

import * as x from "x";
// where 'x' is defined only in `DefinitelyTyped/node_modules`

Good:

Add a package.json:

{
    "private": true,
    "dependencies": {
        "x": "^1.2.3"
    }
}