Enable ESLint for TypeScript files

[leroykorterink]

We should also update the block and smart-component TypeScript templates.

Block:

import AbstractBlock from '../AbstractBlock';

export default class {{name_pc}} extends AbstractBlock {
  public static readonly displayName = '{{name_sc}}';

  public constructor(element:HTMLElement) {
    super(element);
  }

  public dispose() {
    super.dispose();
  }
}

SmartComponent:

import AbstractComponent from '../AbstractComponent';

export default class {{name_pc}} extends AbstractComponent {
  public static readonly displayName = '{{name_sc}}';

  public constructor(element: HTMLElement) {
    super(element);
  }

  public dispose() {
    super.dispose();
  }
}