Doc features: Multicluster

[pushker001]

Helps the user to switch to a different cluster
#255

Check List

• The title of my pull request is a short description of the changes
• This PR relates to some issue:

[undera]

A few notes:

1. Crop screenshot, so there's no huge empty space at the bottom. Also, top side of screenshot is cut in the middle of panel & logo. Either make whole panel & logo visible, or crop it off. Generally, when doing screenshot, think that it is meant to help user locate the element that you describe. For that you need to give some context. So it's better to make screenshot with sufficient surrounding. To summarize, this screenshot should contain full top panel, for context.
2. It's good to add a bit of explanation how this multi-cluster is defined. I mean explaining that the list of clusters comes from kubeconfig. Finding and adding a hyperlink to appropriate k8s doc (https://kubernetes.io/docs/tasks/access-application-cluster/configure-access-multiple-clusters/ in this case) would let reader to continue learning, if needed.