Add a scss file that contains only copyright banner for cherry-picking imports

Created by: ntkme

Prerequisites

• I have searched for duplicate or closed feature requests
• I have read the contributing guidelines

Proposal

Add a banner.scss (or maybe name it copyright.scss or license.scss to avoid confusion) that only contains the copyright information for cherry-picking imports with copyright information.

Motivation and context

I have projects that are cherry-picking a only few scss files from bootstrap to be imported.

I want to properly include the bootstrap copyright header but there is no easy way to do so right now other than manual copy-paste the copyright banner.