Convert part metadata to JSON
We still need to install the desktop file for the KF5 version, and there's some subtle difference between the 5 and 6 metadata, so use JSON directly for 5 and convert .desktop for 6
We still need to install the desktop file for the KF5 version, and there's some subtle difference between the 5 and 6 metadata, so use JSON directly for 5 and convert .desktop for 6