OpenScore lieder corpus v3

This is the first "release" of the OpenScore lieder corpus, backdated to the score upload.
We've used the tag v3.0.0 to reflect the MuseScore version used (3).
Most were transcribed in MuseScore 3 and we leave the trailing .0.0 for any further releases with this state.
We may undertake a batch conversion to MS4 and/or MEI.
Any new releases will be tagged accordingly.

For information about the contents of this repository see the GitHub README and for information about the project, see the README's links to the papers we've written.

This release serves to

• consolidate the transcriptions as they stand in MuseScore 3 (most were transcribed in MuseScore 3)
• free us up to experiment with batch conversion to MS4 and or MEI (see issues)
• mint a DOI via link up with Zenodo to enable direct citation of a repository snapshot.

Thanks as always,
Mark Gotham and Peter Jonas