Add support for Musescore 3.x
The handbook for Musescore 3 mentions this plugin, but the plugin is only compatible with Musescore 2.
Steps to reproduce:
Install in the Musescore 3 plugins folder. Open Musescore 3 Plugins Manager. The addon doesn't show up. Run the plugin in Musescore 3 Plugin Creator. The following error message shows:
Creating component failed
line 16: module "MuseScore" version 1.0 is not installed