Added Docs link in charts of experiments (#103)

* Added docs link in chart-hub for node-drain & core-dns experiment

Signed-off-by: Amit Bhatt <amitbhatt818@gmail.com>

charts/generic/drain-node/drain-node.chartserviceversion.yaml

@@ -32,6 +32,8 @@ spec:
       url: https://kubernetes.io
     - name: Source Code
       url: https://github.com/litmuschaos/litmus/tree/master/experiments/generic
+    - name: Docs
+      url: https://docs.litmuschaos.io/docs/drain-node/
   icon:
     - url: ""
       mediatype: ""