esbuild react starter

Simple react starter using estrella. A few points if you're coming from create-react-app:

• Directly importing CSS files isn't yet supported by esbuild (instead you would have to add it to your public/index.html file)
• create-react-app inlines images for you if you import them, here you would have to add your images to the public directory & then link them accordingly from your js
• Your production build & dev server both use the public directory (you can change this by changing the values in the build.js file)