Port to Musescore 4

[Jojo-Schmitz]

while mantaining ful Mu3 compatibility.
Also some code formatting/indenting.

And adding Chromatic 16Hole harmonica

[jokrefta]

Changing Qt.quit() to quit() seems to have broken Musescore 3 compatibility. I tried this in Musescore 3.6.2 and it doesn't seem to work quite right. When you apply the changes in the popup window it doesn't close it. Plugin Creator shows the error ReferenceError: quit is not defined

[Jojo-Schmitz]

Yes, but that error is harmless.
To close the window other means are available though.

But try (typeof(quit) === 'undefined' ? Qt.quit : quit)()
as taken from https://musescore.org/en/node/337468

[jokrefta]

That seems to work correctly in both versions