add an example for deploying in kubernetes with the strimzi operator

This is a minimal example, the deployment should be tuned.
```
apiVersion: v1
kind: ConfigMap
metadata:
name: burrow-config
data:
burrow.toml: |
[zookeeper]
servers=[ "{{cluster}}-cluster-zookeeper-client.{{namespace}}.svc.cluster.local:2181" ]
timeout=30
root-path="/tmp/zh"
tls="zookeeper"

[tls.zookeeper]
keyfile="/burrow-ca-key/ca.key"
certfile="/burrow-ca-crt/ca.crt"
cafile="/burrow-ca-crt/ca.crt"

[client-profile.default]
kafka-version="2.0.1"
client-id="borrow-client"

[cluster.local]
client-profile="default"
class-name="kafka"
servers=[ "{{cluster}}-cluster-kafka-brokers.{{namespace}}.svc.cluster.local:9092" ]
topic-refresh=60
offset-refresh=30
groups-reaper-refresh=30

[httpserver.default]
address=":8000"
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: burrow
labels:
k8s-app: burrow
spec:
replicas: 1
selector:
matchLabels:
k8s-app: burrow
template:
metadata:
labels:
k8s-app: burrow
annotations:
prometheus.io/scrape: "true"
prometheus.io/port: "8000"
spec:
imagePullSecrets:
- name: {{imagePullSecret}}
containers:
- name: burrow
image: {{registry}}burrow:{{version}}
ports:
- name: api
containerPort: 8000
readinessProbe:
httpGet:
path: /burrow/admin
port: 8000
livenessProbe:
httpGet:
path: /burrow/admin
port: 8000
resources:
limits:
cpu: 100m
memory: 256M
requests:
cpu: 10m
memory: 10M
volumeMounts:
- name: config
mountPath: /etc/burrow/
- name: tmp
mountPath: /tmp
- name: ca-key
mountPath: /burrow-ca-key
- name: ca-crt
mountPath: /burrow-ca-crt
volumes:
- name: config
configMap:
name: burrow-config
- name: ca-key
secret:
secretName: {{cluster}}-cluster-cluster-ca
- name: ca-crt
secret:
secretName: {{cluster}}-cluster-cluster-ca-cert
- name: tmp
emptyDir:
sizeLimit: 10Mi
---
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
name: burrow-network-policy-zookeeper
spec:
ingress:
- from:
- podSelector:
matchLabels:
k8s-app: burrow
ports:
- port: 2181
protocol: TCP
podSelector:
matchLabels:
strimzi.io/cluster: {{cluster}}-cluster
strimzi.io/kind: Kafka
strimzi.io/name: {{cluster}}-cluster-zookeeper
policyTypes:
- Ingress
```

Start by locating the repository's existing deployment or example documentation and compare the proposed ConfigMap, Deployment, and NetworkPolicy with Strimzi conventions. Done means adding a documented minimal Kubernetes example for Burrow that covers the shown placeholders, TLS mounts, probes, and Zookeeper network policy.

Written by the indexing model from the issue text.