New Octane Rule: `no-classic-classes`

Pulled from https://github.com/ember-cli/eslint-plugin-ember/issues/533 which proposes a new set of rules for Octane related best practices

Disallow “classic” classes preferring use of native JS classes

// ### Good
export default class MyComponent extends Component {
  ...
}

// This mixin usage should be okay
export default class MyService extends Service.extends(Evented) {
  ...
}

// ### Bad
export default Component.extend({
  ...
});

If anyone would like to implement this please comment that you’ll take it and work away.

[patocallaghan]

Unfortunately I don’t have admin rights to do that. @bmish could you assign this issue please?

[alexlafroscia]

I’m happy to take this one on – @patocallaghan can you set me as the “assignee”? It’s helpful when browsing the issues and seeing which new rules are yet un-claimed!