Remove unused css

Remove unused css with purgecss.

Do npm run prod:

All unused bootstrap.css styles are removed, only those needed for class="alert alert-danger" component are output in dist/main.css bundle.
.unused-class is removed.
.text-color is placed in the bundle.
.textUnderline is dynamic added in javascript, purgecss detect it and place it in the bundle.
By using safelist option .do_not_remove_this-class will not be removed.

Notes

Purgecss will install node-glob to detect classes.

It works with sass files too.