docs: improve deployment docs in kubernetes. (#2973)

* docs: improve deployment docs in kubernetes.

* move docs path.

* format contents.

* update contents.

* build: update deployment env.

* docs: update deploy docs.

* build: add kafka secret and dependencies.

* docs: update deployment docs.

* Update docs contents.

* update docs contents.

deployments/deploy/redis-secret.yml

@@ -0,0 +1,7 @@
+apiVersion: v1
+kind: Secret
+metadata:
+  name: openim-redis-secret
+type: Opaque
+data:
+  redis-password: b3BlbklNMTIz # "openIM123" in base64