docs: Add funding links and information

Add information on current maintainers, and how users can support the
project.

Author: acoulton

.github/FUNDING.yml

@@ -0,0 +1 @@
+github: [ carlos-granados, stof, acoulton ]

README.md

@@ -52,7 +52,30 @@ curl https://getcomposer.org/installer | php
 php composer.phar update
 ```
 
-## Contributors
+Contributors
+------------
 
-* Konstantin Kudryashov [everzet](http://github.com/everzet) [lead developer]
-* Other [awesome developers](https://github.com/Behat/Gherkin/graphs/contributors)
+- Konstantin Kudryashov [everzet](https://github.com/everzet) [original developer]
+- Andrew Coulton [acoulton](https://github.com/acoulton) [current maintainer]
+- Carlos Granados [carlos-granados](https://github.com/carlos-granados) [current maintainer]
+- Christophe Coevoet [stof](https://github.com/stof) [current maintainer]
+- Other [awesome developers](https://github.com/Behat/Behat/graphs/contributors)
+
+Support the project
+-------------------
+
+Behat is free software, maintained by volunteers as a gift for users. If you'd like to see
+the project continue to thrive, and particularly if you use it for work, we'd encourage you
+to contribute.
+
+Contributions of time - whether code, documentation, or support reviewing PRs and triaging
+issues - are very welcome and valued by the maintainers and the wider Behat community.
+
+But we also believe that [financial sponsorship is an important part of a healthy Open Source
+ecosystem](https://opensourcepledge.com/about/). Maintaining a project like Behat requires a
+significant commitment from the core team: your support will help us to keep making that time
+available over the long term. Even small contributions make a big difference.
+
+You can support [@acoulton](https://github.com/acoulton), [@carlos-granados](https://github.com/carlos-granados) and
+[@stof](https://github.com/stof) on GitHub sponsors. If you'd like to discuss supporting us in a different way, please
+get in touch!