I’m not sure exactly what’s going on there, but if it’s what I think, then check out the rule:

// don't require .vue extension when importing
    'import/extensions': ['error', 'always', {
      js: 'never',
      vue: 'never'
    }],

The ES Lint rule is called “import/extensions”. You can Google it, but the syntax is hopefully as you can see there, except I would use double quotes inside the JSON file :)