Add metadata/notes for each .json file.

[atla5]

would include:

• version of the related standard (ex 'Marc21' specifying a marc.json)
• the references informing the file and that were worked from
• relationship to the official reference (heavily altered/particular implementation --- hybrid --- exact match)
• schema description (expected data, required fields, etc.)
• purpose/relevance/write-up on the standard itself (ex. when/why to use dublin-core)

likely take the format of a .txt (or .md) file, because i don't want to muddy the possibility of reuse of the file itself.