Incorrect import path docs

[deasems]

The readme says to use the script at dist/first-input-delay.js, that file doesn't exist, I think it's meant to be dist/first-input-delay.min.js.

Also consider setting the package main field to the minified version so we can just import from the root of the package. e.g. import fidPolyfillScript from 'raw-loader!first-input-delay'