Add documentation on services deployed to the kube-system namespace

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diff --git a/kubernetes/namespaces/kube-system/README.md b/kubernetes/namespaces/kube-system/README.md
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+# Kubernetes System Namespace
+
+The `kube-system` namespace contains several services used for the operation of
+the Kubernetes cluster.
+
+## Folder Contents
+
+### `coredns-custom.yaml`
+
+This is a custom CoreDNS configuration file loaded in by Linode allowing us to
+add additional configuration options to our cluster DNS server, such as
+additional logging of specific queries.
+
+### `nginx`
+
+This folder contains the deployment of the `ingress-nginx` service which handles
+all inbound traffic to the cluster, TLS termination and forwarding to the
+relevant internal services.
+
+### `reflector`
+
+This is a system component which allows specific annotations on secrets to
+trigger them to replicate to a selected set of other namespaces.
+
+See the README.md in the folder for more information.
+
+## Other components
+
+We deploy the Kubernetes [`metrics-server`](https://github.com/kubernetes-sigs/metrics-server) using the
+manifests specified in the project repository. This allows commands like
+`kubectl top` to work.
+
+We also deploy [`kube-state-metrics`](https://github.com/kubernetes/kube-state-metrics) again using the manifests located in the repository.