Add JSON(other) to the readable config formats

[bdougie]

- Do you want to request a feature or report a bug?
After consultant with a Netlify/Hexo user I found that by default hexo converts yml to json. This can be fixed by adding the admin/config.yml to the skip_render section

- What is the current behavior?
It would be nice to add other formats, like toml or json for the config.

[josephearl]

👍 TOML support would be great for Hugo. Ideally Netlify CMS should be able to read front matter using any supported format and would let me configure which format it writes with.

[erquhart]

@josephearl this issue is about the config file format - the front matter issue you're referring to is covered under #227. Definitely something we'd like to see happen. If you're up for digging in, please comment there, and I'm happy to assist if needed!

[josephearl]

Thanks @erquhart, front matter was what I was after - I'll give #227 a go.

[erquhart]

Closing in favor of #386.