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

[Ulf Hermann]

YAML is really quite terrible. If we're going to switch, let's choose 
something else.

Basically, YAML is extremely complex, ambiguous, and incompatible 
between different versions. See for example 
https://ruudvanasseldonk.com/2023/01/11/the-yaml-document-from-hell for 
an in-depth explanation.

Toml seems to be popular these days.

best regards,
Ulf