Question: Is it possible to index items nested within a data file subfolder?

## How can I index items in a data file subfolder?

For example, using an example from the Jekyll docs, how would I index members specified in `_data/orgs/jekyll.yml` like below?

```
username: jekyll
name: Jekyll
members:
- name: Tom Preston-Werner
github: mojombo

- name: Parker Moore
github: parkr
```

I can't remove the nesting.

### Ruby version used:
2.6.3p62

### Jekyll version used:
4.0.0

Start by reproducing the example with _data/orgs/jekyll.yml and inspect how Jekyll data files are discovered and indexed. Confirm whether the nested members entries are omitted, then define done as making those members searchable without removing the data nesting.

Written by the indexing model from the issue text.