docs: Add instructions for working with Argo CD (#535)

For Argo CD users, provides instructions on how to get around issues encountered when applying KubeRay CRDs.

helm-chart/kuberay-operator/README.md

@@ -46,3 +46,52 @@ $ helm delete kuberay-operator -n ray-system
 
 The command removes nearly all the Kubernetes components associated with the
 chart and deletes the release.
+
+## Working with Argo CD
+
+If you are using [Argo CD](https://argoproj.github.io) to manage the operator, you will encounter the issue which complains the CRDs too long. Same with [this issue](https://github.com/prometheus-operator/prometheus-operator/issues/4439).
+The recommended solution is to split the operator into two Argo apps, such as:
+
+* The first app just for installing the CRDs with `Replace=true` directly, snippet:
+
+```yaml
+apiVersion: argoproj.io/v1alpha1
+kind: Application
+metadata:
+  name: ray-operator-crds
+spec:
+  project: default
+  source:
+    repoURL: https://github.com/ray-project/kuberay
+    targetRevision: v0.3.0
+    path: helm-chart/kuberay-operator/crds
+  destination:
+    server: https://kubernetes.default.svc
+  syncPolicy:
+    syncOptions:
+    - Replace=true
+...
+```
+
+* The second app that installs the Helm chart with `skipCrds=true` (new feature in Argo CD 2.3.0), snippet:
+
+```yaml
+apiVersion: argoproj.io/v1alpha1
+kind: Application
+metadata:
+  name: ray-operator
+spec:
+  source:
+    repoURL: https://github.com/ray-project/kuberay
+    targetRevision: v0.3.0
+    path: helm-chart/kuberay-operator
+    helm:
+      skipCrds: true
+  destination:
+    server: https://kubernetes.default.svc
+    namespace: ray-operator
+  syncPolicy:
+    syncOptions:
+    - CreateNamespace=true
+...
+```