Update README with Tapable.hooks example (#941)
Update README with Tapable.hooks example (#941)

Webpack v4 deprecates the use of `Tapable.plugin()`. This plugin was updated to use `Tapable.hooks`, but the example in the README was not.

ampedandwired/html-webpack-plugin,ampedandwired/html-webpack-plugin,jantimon/html-webpack-plugin,jantimon/html-webpack-plugin