fix references to old variables and to other files

Signed-off-by: paulfantom <pawel@krupa.net.pl>

examples/prometheus-additional-rendered-rule-example.jsonnet

@@ -1,9 +1,15 @@
-local kp = (import 'kube-prometheus/kube-prometheus.libsonnet') + {
-  _config+:: {
-    namespace: 'monitoring',
+local kp = (import 'kube-prometheus/main.libsonnet') + {
+  values+:: {
+    common+: {
+      namespace: 'monitoring',
+    },
   },
-  prometheusAlerts+:: {
-    groups+: (import 'existingrule.json').groups,
+  prometheus+: {
+    prometheusRule+: {
+      spec+: {
+        groups+: (import 'existingrule.json').groups,
+      },
+    },
   },
 };