These options are already set by default to the same values by HTMLWebpackPlugin:
-  collapseWhitespace
-  keepClosingSlash
-  removeComments
-  removeRedundantAttributes
-  useShortDoctype
-  removeStyleLinkTypeAttributes

The other options shouldn't be necessary since we are relying on loaders and
specific plugins to minify.

Webpack already optimize build output in production mode and it seems that its
options are sufficiently good.

Prefer using target's API (ES6 by default), which is more susceptible to be
implemented by browsers.  If one needs more recent ECMAScript feature, he still
can add the needed polyfills and use more recent libs.

We should avoid to include JS files. Only add this option when necessary.

Its is already active when "strict" option is set to true.