Mention stand-alone specs on microprofile.io

[kito99]

When coming to the microprofile.io, it's not clear that non-core specs (ones not shown on the landing page) exist. On the Projects page, some non-core specs are listed, but they're not denoted as such, and they're mixed in with projects like the master bom repo.

From an end-user perspective, I'd like to be able to see all that MicroProfile has to offer, but it's hard to see that from the existing site. Ideally, at a minimum, the Projects page would have all non-core specs, and differentiate between core specs, non-core specs, and others (bom, examples, etc.). I also think the landing page should make it clear that some implementations offer the non-core features as well.