Release 4.1.0: index.js header reports v4.0.0

Created by: volans-

Minor nitpick, it seems that the 4.1.0 release of Bootstrap didn't bump the version of js/src/index.js, that is still reporting:

 * Bootstrap (v4.0.0): index.js

This header line appears also in the following files, that I think are derived from the one in src: