README.md: Add Open Collective (#27864)

Author: monkeywithacupcake

README.md

@@ -66,6 +66,8 @@ Read the [Getting started page](https://getbootstrap.com/docs/4.1/getting-starte
 [![CSS gzip size](https://img.badgesize.io/twbs/bootstrap/v4-dev/dist/css/bootstrap.min.css?compression=gzip&label=CSS+gzip+size)](https://github.com/twbs/bootstrap/tree/v4-dev/dist/css/bootstrap.min.css)
 [![JS gzip size](https://img.badgesize.io/twbs/bootstrap/v4-dev/dist/js/bootstrap.min.js?compression=gzip&label=JS+gzip+size)](https://github.com/twbs/bootstrap/tree/v4-dev/dist/js/bootstrap.min.js)
 [![BrowserStack Status](https://www.browserstack.com/automate/badge.svg?badge_key=SkxZcStBeExEdVJqQ2hWYnlWckpkNmNEY213SFp6WHFETWk2bGFuY3pCbz0tLXhqbHJsVlZhQnRBdEpod3NLSDMzaHc9PQ==--3d0b75245708616eb93113221beece33e680b229)](https://www.browserstack.com/automate/public-build/SkxZcStBeExEdVJqQ2hWYnlWckpkNmNEY213SFp6WHFETWk2bGFuY3pCbz0tLXhqbHJsVlZhQnRBdEpod3NLSDMzaHc9PQ==--3d0b75245708616eb93113221beece33e680b229)
+[![Backers on Open Collective](https://opencollective.com/bootstrap/backers/badge.svg)](#backers)
+[![Sponsors on Open Collective](https://opencollective.com/bootstrap/sponsors/badge.svg)](#sponsors)
 
 
 ## What's included
@@ -181,6 +183,29 @@ See [the Releases section of our GitHub project](https://github.com/twbs/bootstr
 Thanks to [BrowserStack](https://www.browserstack.com/) for providing the infrastructure that allows us to test in real browsers!
 
 
+## Backers
+
+Thank you to all our backers! 🙏 [[Become a backer](https://opencollective.com/bootstrap#backer)]
+
+[![Bakers](https://opencollective.com/bootstrap/backers.svg?width=890)](https://opencollective.com/bootstrap#backers)
+
+
+## Sponsors
+
+Support this project by becoming a sponsor. Your logo will show up here with a link to your website. [[Become a sponsor](https://opencollective.com/bootstrap#sponsor)]
+
+[![](https://opencollective.com/bootstrap/sponsor/0/avatar.svg)](https://opencollective.com/bootstrap/sponsor/0/website)
+[![](https://opencollective.com/bootstrap/sponsor/1/avatar.svg)](https://opencollective.com/bootstrap/sponsor/1/website)
+[![](https://opencollective.com/bootstrap/sponsor/2/avatar.svg)](https://opencollective.com/bootstrap/sponsor/2/website)
+[![](https://opencollective.com/bootstrap/sponsor/3/avatar.svg)](https://opencollective.com/bootstrap/sponsor/3/website)
+[![](https://opencollective.com/bootstrap/sponsor/4/avatar.svg)](https://opencollective.com/bootstrap/sponsor/4/website)
+[![](https://opencollective.com/bootstrap/sponsor/5/avatar.svg)](https://opencollective.com/bootstrap/sponsor/5/website)
+[![](https://opencollective.com/bootstrap/sponsor/6/avatar.svg)](https://opencollective.com/bootstrap/sponsor/6/website)
+[![](https://opencollective.com/bootstrap/sponsor/7/avatar.svg)](https://opencollective.com/bootstrap/sponsor/7/website)
+[![](https://opencollective.com/bootstrap/sponsor/8/avatar.svg)](https://opencollective.com/bootstrap/sponsor/8/website)
+[![](https://opencollective.com/bootstrap/sponsor/9/avatar.svg)](https://opencollective.com/bootstrap/sponsor/9/website)
+
+
 ## Copyright and license
 
 Code and documentation copyright 2011-2018 the [Bootstrap Authors](https://github.com/twbs/bootstrap/graphs/contributors) and [Twitter, Inc.](https://twitter.com) Code released under the [MIT License](https://github.com/twbs/bootstrap/blob/master/LICENSE). Docs released under [Creative Commons](https://github.com/twbs/bootstrap/blob/master/docs/LICENSE).