docs: Add kind doc for users

[sknat]

This patch adds documentation on how to set up a kind cluster with calico/vpp & multinet installed, without requiring to build VPP locally or to have the whole repository cloned locally.

This should work without requiring to run any remote script.

[hedibouattour]

Tested it, it works fine, lgtm.

[sknat]

Probably worth adding a how to try kind without multinet