Add Supplier Exporter sample

spring-cloud-function-samples/function-sample-supplier-exporter/README.md

@@ -0,0 +1,16 @@
+AWS Lambda custom runtime.
+
+```
+$ ./build.sh
+$ ./mvnw package -P native
+```
+ 
+builds a native-zip ZIP file in target. Upload it to AWS and set the handler to "foobar".
+
+To test locally, run the `TestServer` and then the `DemoApplication` (either in a JVM or natively). Then POST some data into the test server:
+
+```
+$ curl localhost:8000/add -d world -H "Content-Type: text/plain"
+```
+
+There is a unit test that does the same thing. Also the `build.sh` script orchestrates the same test for the native image.