add tvb-widgets as a spack package
Issue 8 (https://gitlab.ebrains.eu/ri/projects-and-initiatives/ebrains-2/wp3/tc/-/issues/8): tvb-widgets as Spack
Issue 8 (https://gitlab.ebrains.eu/ri/projects-and-initiatives/ebrains-2/wp3/tc/-/issues/8): tvb-widgets as Spack