Example of shared-everything linking

After some [discussion on Zulip](https://bytecodealliance.zulipchat.com/#narrow/channel/219900-wasi/topic/bundling.20shared-everything.20libraries/near/513881833)[#wasi > bundling shared-everything libraries @ 💬](https://bytecodealliance.zulipchat.com/#narrow/channel/219900-wasi/topic/bundling.20shared-everything.20libraries/near/513881833), an example repository + link in the "Advanced Topics" section might be nice for shared-everything linking.

This is *certainly* a very advanced topic but it would be useful to have it included, to head-off questions of how to do it.

Review the existing "Advanced Topics" section and the linked Zulip discussion first. Done means adding a shared-everything linking example repository and linking to it from that section.

Written by the indexing model from the issue text.