add note about free licenses to readme

Author: psifertex

README.md

@@ -66,3 +66,7 @@ Oddly enough GitHub actions requires the distributed bundle to be in-tree, when
 
 [Binary Ninja]: https://binary.ninja
 [act]: https://github.com/nektos/act
+
+## Free License
+
+Are you maintaining an open source plugin that could use a dedicated headless license to run test or build processes in an automated action? Contact [support](https://binary.ninja/support)! For qualified plugins and developers we make free licenses available for just such a purpose.