Extend schemas to support single files

[hunvreus]

Currently schemas are mostly geared towards helping users create/manage collections: pages, posts...

We should consider starting to support schema declarations that apply to a single file. For example for _config.yml or data files (in the data/ subfolder).

[JuhaS]

@hunvreus how would Jekyll process these files, anything relevant we should know here? We currently have this as part of schema def, what would make sense for these fields (do we even need them?):

  ...
  "jekyll": {
    "type": "content",
    "id": "posts",
    "dir": "_posts"
  },
  ...

[hunvreus]

Probably (also integrating #56);

• Collection;

  "title": "Products",
  "description": "Any food, beverage or tea product (e.g. Frappuccino, Muffin...)."
  "jekyll": {
      "type": "collection",
      "id": "products",
      "dir": "_products",
      "format": "html"
  },

• Single file;

  "title": "Navigation",
  "description": "A simple configuration file for the navigation."
  "jekyll": {
      "type": "file",
      "id": "config",
      "path": "_data/nav.yml",
      "format": "yml"
  },

  "title": "Sitemap",
  "description": "The XML sitemap file for the whole site."
  "jekyll": {
      "type": "file",
      "id": "config",
      "path": "sitemap.xml",
      "format": "plain"
  },

For the second item I think we have to be explicit with the type of editor; we can't just guess from the file extension what to do.

[hunvreus]

Scratch that: we just need to have a way to list files with an associated Title and Description. It will link to the GitHub edit page.