`bs-custom-file-input` doesn't work anymore since the form updates

Created by: MartijnCuppens

https://twbs-bootstrap.netlify.com/docs/5.0/forms/file/ broke since the class names aren't identical anymore.

Also, imo the plugin should be part of Bootstrap by default, since the file input's don't work without it. Also this should work out of the box without initializing it, this will be way more flexible if content is added to the DOM async.