Local itk-vtk-viewer

It is ready to install the itk-viewer in case it is not installed in qim https://www.notion.so/qim-dtu/Improve-CLI-viz-f4254522fa1e4159b8ce6d9206793b13

qim3d/viz/itk_vtk_viewer/__init__.py

-from .installation import install_viewer
-from .run import run_viewer
\ No newline at end of file
+from .installation import Installer
+from .run import run_viewer
+from .helpers import NotInstalledError
\ No newline at end of file