Save folder collection entries to single data file

Middleman has an excellent feature whereby you can generate all of your content via a single [data file](https://middlemanapp.com/advanced/data-files/). If used in conjunction with [Dynamic pages](https://middlemanapp.com/advanced/dynamic-pages/) this becomes a beautifully simple yet powerful setup.

If Netlify CMS could support creating & editing these simple YAML or JSON entries that would be a highly leveraged way to author a static site while enabling easy access to other services & APIs.

I have considered more enterprise headless CMS solutions for example [Prismic.io](https://prismic.io/) however it feels like overkill for this kind of use case.

This may be achievable with a new collection type "data" as a close cousin to the folder collection type.

Thank you for your consideration.