Add Open Collective badge

Author: Flo

README.md

@@ -1,5 +1,5 @@
 # Open Climate Fix Website
-[![All Contributors](https://img.shields.io/badge/all_contributors-5-orange.svg?style=flat-square)](#contributors-)
+[![All Contributors](https://img.shields.io/badge/all_contributors-5-orange.svg?style=flat-square)](#contributors-) [![Open Collective backers and sponsors](https://img.shields.io/opencollective/all/openclimatefix?style=flat-square)](https://opencollective.com/openclimatefix)
 
 Source for openclimatefix.org.
 This is currently under heavy construction.
@@ -27,4 +27,4 @@ Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/d
 <!-- prettier-ignore-end -->
 <!-- ALL-CONTRIBUTORS-LIST:END -->
 
-This project follows the [all-contributors](https://github.com/all-contributors/all-contributors) specification. Contributions of any kind welcome!
+This project follows the [all-contributors](https://github.com/all-contributors/all-contributors) specification. Contributions of any kind welcome!