scaffolding for typescript (#3504)

* scaffolding for typescript

* add jest types so tests will compile

* remove rollup-plugin-typescript2, probably don't need it

* add missing eslint-import

* fix linting errors

todomvc/src/components/App.spec.js

@@ -4,8 +4,7 @@ import App from './App'
 import Header from '../containers/Header'
 import MainSection from '../containers/MainSection'
 
-
-const setup = propOverrides => {
+const setup = _propOverrides => {
   const renderer = createRenderer()
   renderer.render(<App />)
   const output = renderer.getRenderOutput()
@@ -16,16 +15,16 @@ describe('components', () => {
   describe('Header', () => {
     it('should render', () => {
       const output = setup()
-      const [ header ] = output.props.children
+      const [header] = output.props.children
       expect(header.type).toBe(Header)
     })
   })
-  
+
   describe('Mainsection', () => {
     it('should render', () => {
       const output = setup()
-      const [ , mainSection ] = output.props.children
+      const [, mainSection] = output.props.children
       expect(mainSection.type).toBe(MainSection)
     })
   })
-})
+})