feat: Add new Geometry Nodes groups for image relief and shadeless shader

- Implemented the "O Image Relief Plane" Geometry Nodes group to create a fixed-base image relief using depth images and various parameters.
- Created the "O Shadeless" shader node group to display color without scene lighting while preserving shadows and reflections.
- Introduced a preview feature for node groups, allowing for interactive visualization of node arrangements in an HTML format.
- Added a template HTML file for rendering node previews with customizable views and controls.

tests/test_addon_registration.py

@@ -21,6 +21,7 @@ class AddonRegistrationTest(BlenderTestCase):
         operator = self.convert_to_plane.ConvertToPlane
         self.assertIn(operator, self.anyimage.CLASSES)
         self.assertIn(self.convert_to_plane.ConvertToDepthPlane, self.anyimage.CLASSES)
+        self.assertIn(self.convert_to_plane.ConvertToReliefPlane, self.anyimage.CLASSES)
         self.assertFalse(hasattr(self.convert_to_plane, "ConvertToDepthSurface"))
         self.assertIn(self.cutout_main.CutoutSelectionToShape, self.anyimage.CLASSES)
         self.assertEqual(operator.bl_idname, "anyimage.convert_to_plane")