Fix theme CSS regression.

Noticed on `enwiki > Javascript`. The collapsed tables borders were gone when using sepia or dark themes.

Caused by using the '-p' webpack switch, which caused the CSS to be minified ( webpack-contrib/html-loader#65 (comment) ), which changed the order of CSS, which was important. Specifically, the `ThemeTransform` CSS needs to be 1st, as outlined here https://github.com/wikimedia/wikimedia-page-library/blob/master/src/transform/index.js#L3 and here #128 (comment)

webpack.config.babel.js

@@ -55,7 +55,7 @@ const config = {
             loader: 'style-loader',
             options: { hmr: false }
           },
-          use: [{ loader: 'css-loader' }, 'postcss-loader']
+          use: [{ loader: 'css-loader', options: { minimize: false } }, 'postcss-loader']
         })
       }
     ]