Add new node asset scripts for geometry and shader operations

- Implemented `build_mesh_plane.py` to create a geometry node group for mesh planes with customizable parameters.
- Created `build_shadeless.py` for a shader node group that displays color without scene lighting while preserving shadows and reflections.
- Added `validate.py` to validate the integrity of the newly created node groups and their inputs.
- Introduced `validate_cutout.py` to ensure the functionality of cutout node groups and their dependencies.
- Developed `validate_mesh_plane.py` to test the mesh plane creation and its modifier settings.

src/anyimage/blender_manifest.toml

@@ -20,5 +20,6 @@ files = "Read source and clipboard images, and store environment data"
 paths_exclude_pattern = [
   "__pycache__/",
   ".*",
+  "*.blend[0-9]*",
   "*.zip",
 ]