Viz add colorbar

https://www.notion.so/qim-dtu/Add-colorbar-to-vizualisation-tools-a1b4cb67bd4a4de39a7ac40bf5d35fd5

qim3d/viz/explore.py

@@ -186,7 +186,7 @@ def slices(
     if cbar:
         norm = matplotlib.colors.Normalize(vmin=vmin, vmax=vmax, clip=True)
         mappable = matplotlib.cm.ScalarMappable(norm=norm, cmap=cmap)
-        fig.colorbar(mappable=mappable, ax=axs, orientation='vertical')
+        fig.colorbar(mappable=mappable, ax=np.atleast_1d(axs[0])[-1], orientation='vertical')
 
     if show:
         plt.show()