Add "unassigned" to importType for order rule

I would like to group and order unassigned imports. This specific use case is for importing Polymer 2 html elements with polymer-webpack-loader.

import { Component } from '@angular/core';

import 'bower_components/paper-button/paper-button.html';

import { value } from '../parent'; 
import { other } from './sibling';

The proposed .eslintrc to achieve the above style would be

"import/order": [
  "error", 
  {
    "groups": ["builtin", "external", "unassigned", ["parent", "sibling", "index"]],
    "newlines-between": "always"
  }
]

At the moment unassigned imports are completely ignored.

[constgen]

@ljharb As I described above sometimes it may be important. Preserving the necessary order for the particular project may be highly necessary. To not make breaking changes I propose to add an option to pathGroups so consumers may enable processing of side affect imports for certain groups. E.g.:

"pathGroups": [
  {
    "pattern": "{.,..}/**/*.+(css|sass|less|scss|pcss|styl)",
    "unnamed": true, // this is a new option
    "group": "unknown",
    "position": "after"
  }
]

[ljharb]

This seems reasonable; altho I’d call them “side-effecting” or something instead of just “unassigned”.

A use case that isn’t deprecated (ie, that doesn’t involve bower) would be shimming/polyfilling.