ipn/store: add ability to store data as k8s secrets.

Signed-off-by: Maisem Ali <maisem@tailscale.com>

docs/k8s/README.md

@@ -0,0 +1,20 @@
+# Using Kubernetes Secrets as the state store for Tailscale
+Tailscale supports using Kubernetes Secrets as the state store, however there is some configuration required in order for it to work.
+
+**Note: this only works if `tailscaled` runs inside a pod in the cluster.**
+
+1. Create a service account for Tailscale (optional)
+   ```
+   kubectl create -f sa.yaml
+   ```
+
+1. Create role and role bindings for the service account
+   ```
+   kubectl create -f role.yaml
+   kubectl create -f rolebinding.yaml
+   ```
+
+1. Launch `tailscaled` with a Kubernetes Secret as the state store.
+   ```
+   tailscaled --state=kube:tailscale
+   ```