add supported k8s version check

internal/config/errors.go

@@ -0,0 +1,11 @@
+package config
+
+import "fmt"
+
+type UnsupportedK8sVersion struct {
+	Version string
+}
+
+func (e *UnsupportedK8sVersion) Error() string {
+	return fmt.Sprintf("kubernetes version %s is not supported\n\ncurrently supported: %v", e.Version, kubernetesVersions)
+}