add usage examples

closes #1

examples/exec-krm/README.md

@@ -0,0 +1,17 @@
+# Exec Plugin Example
+
+This example runs `YqTransformer` as an **exec KRM function**.
+
+## Locate the plugin executable
+
+The `config.kubernetes.io/function` annotation in `yq-transformer.yaml`
+points to the plugin's executable path in the `exec.path` key.
+This path is relative to `kustomization.yaml` and can be anywhere on disk.
+
+## Build with alpha plugins and exec enabled
+
+```bash
+kustomize build --enable-alpha-plugins --enable-exec .
+```
+
+You should see a label `environment: dev` added to one of the Deployments.