Document how to make a multi site configuration

[bryopsida]

We currently only document a single site setup, it should be possible to use multiple deployments each connecting to each other.

Specifically this scenario

                A
              |   |
            |       |
          |           |
         B             C

B cluster can route/connect to A but its clients cannot directly route to A
B cluster cannot route directly to C
C cluster can route/connect to A but its clients cannot directly route to A
C cluster cannot route directly to B

B site connects to A
C site connects to A

cluster service discovery is not available to peers as that would likely require deconflicting the cluster domains and routing dns to the appropriate kube dns or synchronizing entries using something such as external-dns and extending the cluster dns with record synchronized across the nodes via that.

B peers can connect C peers and vice versa, WAN egress could go through A.

[bryopsida]

Likely would need to add something to share peer routes across WG server pods in same cluster.