docs/customizations: Move customization examples to dedicated folder

With the objective of improving our README, customization examples are being moved to a dedicated folder under `docs/`.

Signed-off-by: ArthurSens <arthursens2005@gmail.com>

docs/customizations/monitoring-all-namespaces.md

@@ -0,0 +1,29 @@
+### Monitoring all namespaces
+
+In case you want to monitor all namespaces in a cluster, you can add the following mixin. Also, make sure to empty the namespaces defined in prometheus so that roleBindings are not created against them.
+
+```jsonnet mdox-exec="cat examples/all-namespaces.jsonnet"
+local kp = (import 'kube-prometheus/main.libsonnet') +
+           (import 'kube-prometheus/addons/all-namespaces.libsonnet') + {
+  values+:: {
+    common+: {
+      namespace: 'monitoring',
+    },
+    prometheus+: {
+      namespaces: [],
+    },
+  },
+};
+
+{ ['00namespace-' + name]: kp.kubePrometheus[name] for name in std.objectFields(kp.kubePrometheus) } +
+{ ['0prometheus-operator-' + name]: kp.prometheusOperator[name] for name in std.objectFields(kp.prometheusOperator) } +
+{ ['node-exporter-' + name]: kp.nodeExporter[name] for name in std.objectFields(kp.nodeExporter) } +
+{ ['kube-state-metrics-' + name]: kp.kubeStateMetrics[name] for name in std.objectFields(kp.kubeStateMetrics) } +
+{ ['alertmanager-' + name]: kp.alertmanager[name] for name in std.objectFields(kp.alertmanager) } +
+{ ['prometheus-' + name]: kp.prometheus[name] for name in std.objectFields(kp.prometheus) } +
+{ ['grafana-' + name]: kp.grafana[name] for name in std.objectFields(kp.grafana) }
+```
+
+> NOTE: This configuration can potentially make your cluster insecure especially in a multi-tenant cluster. This is because this gives Prometheus visibility over the whole cluster which might not be expected in a scenario when certain namespaces are locked down for security reasons.
+
+Proceed with [creating ServiceMonitors for the services in the namespaces](monitoring-additional-namespaces.md#defining-the-servicemonitor-for-each-additional-namespace) you actually want to monitor