Added all-contributors section to README.md

Author: SableRaf

README.md

@@ -62,3 +62,14 @@ For complete licensing information about the Processing core library and softwar
 For licensing information about the Processing website see the [processing-website README](https://github.com/processing/processing-website/blob/main/README.md#licenses).
 
 Copyright (c) 2015-now The Processing Foundation
+
+## Contributors
+
+<!-- ALL-CONTRIBUTORS-LIST:START - Do not remove or modify this section -->
+<!-- prettier-ignore-start -->
+<!-- markdownlint-disable -->
+
+<!-- markdownlint-restore -->
+<!-- prettier-ignore-end -->
+
+<!-- ALL-CONTRIBUTORS-LIST:END -->