Add an example function to append an Application CR to resources

functions/examples/application-cr/README.md

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+# Append Application CR
+
+This is an example of appending an Application CR to a group of resources.
+
+This example is written in `go` and uses the `kyaml` libraries for parsing the
+input and writing the output.  Writing in `go` is not a requirement.
+
+## Function implementation
+
+The function is implemented as an [image](image), and built using `make image`.
+
+The template is implemented as a go program, which reads a collection of input
+Resource configuration, and looks for invalid configuration.
+
+## Function invocation
+
+The function is invoked by authoring a [local Resource](local-resource)
+with `metadata.annotations.[config.kubernetes.io/function]` and running:
+
+    kustomize config run local-resource/ --fn-path config/
+
+This exits non-zero if there is an error.
+
+## Running the Example
+
+Run the validator with:
+
+    kustomize config run local-resource/ --fn-path config/
+
+This will append an Application CR.