Explore integrating GitHub issues into documentation

[jpmckinney]

We might tag issues with specific labels, that can then be rendered in the documentation. The simple implementation of this depends on being able to use the GitHub API on the client side. A more complex implementation would involve creating a middleware API that serves up issues by label, for the documentation to render.

For example, #322 #438 #872

Suggested by @yolile

[jpmckinney]

I think the only robust way to do this is to manually add links to issues in the documentation (as we've started to do in several worked examples). Otherwise, we'll have to support a very large number of labels, in order to allow the issue links to appear everywhere relevant in the docs, which will be a very complicated system to use.