feat: use data from custom collections when using prototypes

[luctus]

Summary

Hey! I'm loading all the data from external API, so everything lives under my site.collections hash. When using a prototype, I'm trying to pull some labels from the collection to use it as the page title, with the :prototype-data-label variable, but it fails.

Guide-level explanation

When using prototypes, you can declare two arguments in the Front Matter segment, like this:

---
layout: default
title: Articles by :prototype-data-label
prototype:
  term: author
  data: authors
  data_label: name
---

However, the prototype generator will only look for that label at the site.data hash, for example: site.data[:authors][term][:name]. If you loaded the data from an external API, this data will be accessable at the site.collections hash, not at the site.data one.

Reference-level explanation

I reckon we could add something here so if we don't find anything at site.data, we can try at the site's collections before returning.

Drawbacks

I don't see any drawbacks, to be honest.

Unresolved Questions

No questions so far.

[jaredcwhite]

Makes sense…we could probably leverage the Relations API here so that the prototype page would pull in the join data through a named relation.