Prefix publicPath missing

[wallzero]

The favicons are inserted into the given publicPath option in webpack.config.js, but the generated index.html URL's are missing the prefixed public path.

[Devin R. Olsen]

Due to the order of Webpack process assets, we must first accept incoming HTML from html-webpack-plugin, then inject the HTML generated by favicon lib into the head of the html-webpack-plugin markup.

This means we lose the opportunity for publicPath fixing done by html-webpack-plugin, but instead must do it manually.
I've dropped in a check for if webpack configuration has a defined publicPath, and if so, prepend it to the start of any href="" in the generated favicon markup.

Thanks again!