JSON: Support max-width (and size-unit) rules

[Chase Tingley]

We’ve got an interest in supporting the ability to flag JSON keys as providing max-width and size-unit information, using a similar mechanism to noteRules and subfilterRules.

Example:

{
    "content": {
        "text": "This is what you have to translate",
        "max": "325",
        "description": "This is metadata"
    },
        "content": {
        "text": "This is what you have to translate, second sentence.",
        "max": "100",
        "description": "This is also metadata"
    }
}

In this case, we would want to have the value of max extracted as an XLIFF max-width property.

Some of the details here may need to be thought through, but I’m filing this before I forget.