qmlformat: Read files from file

We want to format all of our files at once and check that on correct formatting on CI. It would be helpful for our buildsystem to generate a "file" with all qml files as content.

This avoids a too large cmdline with all files as parameter as it is limited.

We use that mechanism for uncrustify:

/usr/bin/uncrustify -c uncrustify.cfg --replace --no-backup -q -F ./formatting.files

$ uncrustify --help
 -F FILE      : Read files to process from FILE, one filename per line (- is stdin).
...

https://github.com/uncrustify/uncrustify