Added class alias for bespoke.js so added string-replace-loader before postcss-loader.
__body -> .bespoke-parent
__bg -> .bespoke-backdrop
__section-title -> .bespoke-backdrop.section-title
Sample: https://github.com/hiroppy/fusuma/blob/master/samples/fx/style.css
Also, it will not convert anything other than specific keys, so it has backward compatibility.