[ENHANCEMENT] Expose the underlying BCD data to explain _why_ something isn't available

**Is your feature request related to a problem? Please describe.**
This is rather related to https://github.com/GoogleChrome/webstatus.dev/issues/277, but this is really a request to expose some of the underlying data in some way, similar to https://github.com/web-platform-dx/web-features-explorer/issues/56.

If you look at https://webstatus.dev/features/marker, and you know Safari has support for `::marker`, you might reasonably ask "why is this not available in Safari".

If you know too much about WebDX and Web Features tooling, you might realise you should look at https://github.com/web-platform-dx/web-features/blob/v2.36.1/features/marker.yml.dist (which tells you that none of the BCD keys are supported in Safari) and then https://github.com/mdn/browser-compat-data/blob/v6.0.20/css/selectors/marker.json (which tells you one of them has "partial support", and one is unsupported, albeit the latter fixed since the latest BCD release in https://github.com/mdn/browser-compat-data/commit/baee315859d81b93968c690c14823fb60499a685).

But this requires you to know a lot about how this all fits together to find the relevant pieces — and the "Incorrect Data" issue template only does so much to direct you here.

This also potentially makes it easier to find things where a feature has long-term partial support (c.f. https://github.com/web-platform-dx/web-features/issues/915), which is potentially indicative of a feature which should be split into smaller sub-features.

**Describe the solution you'd like**
Exposing the individual BCD items on the individual feature pages would be nice, potentially in a table similar to how MDN displays them. This would make it a lot easier to understand why something is being deemed to be available or not.

**Describe alternatives you've considered**
Do nothing. Rely on users to click through from the feature page to "Report an Issue", open the "Incorrect Data" template, follow the cross-references and hopefully find what you're looking for (though note https://github.com/GoogleChrome/webstatus.dev/issues/1515 and https://github.com/mdn/mdn/issues/681 makes this hard and relies on people to know how a lot of this fits together to find the underlying data!).