XML schema or msbuild targets in VSIX v3

Hello,

I found these old questions Installing XML schemas files (*.xsd) with VSIX and When will VSIX packages support deploying MSBuild extensions? asking for the same in 2010, but if I understand correctly the documentation, in VSIX v3, it should be possible to install files outside of the extensions folder.

However, the documentation only deals with ProjectReferences. How do I add an individual .xsd file asset and specify it should go to [INSTALLDIR]\Xml\Schemas in the vsixmanifest?

Thanks,
Jan