Provide "links" from our extension API docs to sample usage

[eamodio]

Refs: #93604

Our Extension API docs, don't provide/link to examples for how they should be use. It would be great if we provided some sort of link between the API docs and our samples.

We do have this Extension Guides Overview page, which kind of provides some of this, but almost in reverse.

Another idea floated by @kieferrm was to use LSIF in product to provide a sort of "find usages" help to the API directly in the editor -- where we might use LSIF snapshots for popular/good examples of OSS extensions using the particular API.