Fix compatibility with vue-meta (htmlAttrs, bodyAttrs, ...)

[frankfoerster]

Version: v0.5.0

Problem

The plugin currently minifies the html template and converts all characters to lowercase.

This breaks compatibility with some of the meta injections vue-meta offers, e.g.:
{{{ meta.inject().htmlAttrs.text() }}} and {{{ meta.inject().bodyAttrs.text() }}}.

When using those in the index.html template, the build step minifies and lowercases it, resulting in
{{{ meta.inject().htmlattrs.text() }}} and {{{ meta.inject().bodyattrs.text() }}}.

As a result the server-side rendering process throws an error (500) because it cannot resolve htmlattrs/bodyattrs.

Solution

a) Enable case sensitivity for the minification step on the html webpack plugin.
b) Make the options configurable via plugin config.

Pull request for a) follows.