New dictionary format

[uga-rosa]

There is a request to be able to use a dictionary with a set of words and descriptions.
Since I do not want to parse the dictionary in a proprietary format, the json format, which can be used with vim.json, is the preferred format for structuring the dictionary.
If the dictionary file extension is not .json, it can be regarded as a dictionary as before, so compatibility can be maintained.

[uga-rosa]

Is there anything else needed in the fields for each word other than WORD and DESCRIPTION?