docs: Add docs for path prefix deploy example

deploy/kubectl/path-prefix/Readme.md

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+# Deploy kube-explorer behind proxy with path prefix
+
+> Supported since v0.5.0
+
+The kube-explorer dashboard can be exposed behind a proxy and path prefix like `http://your-domain.com/kube-explorer`.
+
+The deployment examples in this folder are:
+
+- `nginx ingress`
+- `traefik ingress`
+
+## Serve with ingress
+
+When serving with nginx/traefik ingress controller, the template ingress file needs to be modified. In the `*.tpl` file, you can spot the missing hostname like:
+
+```yaml
+spec:
+  rules:
+    - host: "${MY_IP}.sslip.io" # Replace with your actual domain
+```
+
+Replace your ip to `${MY_UP}`, this will use the [sslip.io](https://sslip.io/) dns service to resolve the hostname to the ingress ip address.
+
+For the traefik ingress, it is using `v2` version of the traefik ingress schema which use middlewares to modify the proxy request. Both `stripPrefix` and `headers` are used.  
+For the nginx ingress, the annotations `nginx.ingress.kubernetes.io/x-forwarded-prefix` and `nginx.ingress.kubernetes.io/rewrite-target` are used to strip prefix and to add proxy request header.
+
+## Serve with self-hosted proxy
+
+If serving the kube-explorer with self-hosted proxy, following modifications are required when proxying:
+
+- Rewrite the proxy request to strip the path prefix like `rewrite "(?i)/kube-explorer(/|$)(.*)" /$2 break;` in nginx configuration.
+- Add header `X-API-URL-Prefix` or `X-Forwarded-Prefix` with the path prefix when proxying request like `proxy_set_header X-Forwarded-Prefix "/kube-explorer";` in nginx configuration.
+
+Then kube-explorer will response the index.html with modified content with path prefix to the browser.

deploy/kubectl/path-prefix/nginx-ingress.yaml.tpl

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+# Note: please replace the host first
+# To use sslip.io: https://sslip.io/
+# To get your public IP: curl ipinfo.io/ip
+apiVersion: networking.k8s.io/v1
+kind: Ingress
+metadata:
+  annotations:
+    nginx.ingress.kubernetes.io/x-forwarded-prefix: "/kube-explorer"
+    nginx.ingress.kubernetes.io/rewrite-target: /$2
+  name: kube-explorer-ingress
+  namespace: kube-system
+spec:
+  rules:
+    - host: "${MY_IP}.sslip.io" # Replace with your actual domain
+      http:
+        paths:
+          - backend:
+              service:
+                name: kube-explorer
+                port:
+                  name: http
+            path: /kube-explorer(/|$)(.*)
+            pathType: ImplementationSpecific
+

deploy/kubectl/path-prefix/traefik-ingress.yaml.tpl

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+# Note: please replace the host first
+# To use sslip.io: https://sslip.io/
+# To get your public IP: curl ipinfo.io/ip
+apiVersion: networking.k8s.io/v1
+kind: Ingress
+metadata:
+  name: kube-explorer-ingress
+  namespace: kube-system
+  annotations:
+    traefik.ingress.kubernetes.io/router.middlewares: kube-system-prefix@kubernetescrd,kube-system-add-header@kubernetescrd
+spec:
+  rules:
+  - host: "${MY_IP}.sslip.io"  # Replace with your actual domain
+    http:
+      paths:
+      - path: /kube-explorer
+        pathType: Prefix
+        backend:
+          service:
+            name: kube-explorer
+            port:
+              name: http
+---
+apiVersion: traefik.io/v1alpha1
+kind: Middleware
+metadata:
+  name: prefix
+  namespace: kube-system
+spec:
+  stripPrefix:
+    prefixes:
+      - /kube-explorer
+---
+apiVersion: traefik.io/v1alpha1
+kind: Middleware
+metadata:
+  name: add-header
+  namespace: kube-system
+spec:
+  headers:
+    customRequestHeaders:
+      X-Forwarded-Prefix: "/kube-explorer" # Adds