message: Add opencollective contributor images
diff: @@ -103,6 +103,6 @@ all the ways in which you can help out with the project, as well as provides
  detailed instructions for building and hacking on Enso.
  <a href="https://github.com/luna/enso/graphs/contributors">
  - <img src="https://contributors-img.firebaseapp.com/image?repo=luna/enso" />
  + <img src="https://opencollective.com/enso-language/contributors.svg?width=890&button=false">
  </a>
  