[Development] Support for *Notes and UpstreamFiles fields in qt_attributions.json files

[Ulf Hermann]

> QML supports comments, but not multi-line string literals. You can concatenate
> them, though.

Sure it does. You can use ECMAScript template strings:

property string longthing: `a multi
                             line string`

(In fact you can also just sprinkle line breaks into your regular 
strings. But don't.)