code: function transformDefaultClassExports(content) {
    return content.replace(/^(\s*)export default (abstract )?class ([\w]+)/mg, function(m0, m1, m2, m3) {
      return m1 + 'export { ' + m3 + ' as default, ' + m3 + ' };\n' +
        m1 + (m2 || '') + 'class ' + m3
    })
  }
docs: changes the name of the default export to `Default` and exports it as a *named* export. this allows ambient declaration merging to grab onto it. workaround for https://github.com/Microsoft/TypeScript/issues/14080 NEEDED ANYMORE?