Update README.md with sponsroship info

Author: wing328

apps/generator-cli/src/README.md

@@ -12,6 +12,8 @@ configuration automatically given an OpenAPI Spec (both 2.0 and 3.0 are supporte
 
 The OpenAPI Generator is a Java project. `openapi-generator-cli` will download the approprate JAR file and invoke the `java` executable to run the OpenAPI Generator. You must have the `java` binary executable available on your `PATH` for this to work.
 
+If you find this tool useful, please consider sponsoring this project financially via https://opencollective.com/openapi_generator or directly to [Kay Schecker](https://github.com/sponsors/kay-schecker) (the author of this tool) :pray:
+
 ---
 
 ## Version 2.x.x