Add tools and tests for AnyImage model management and documentation

- Implement sync_models.py for preparing and uploading ONNX artifacts.
- Create build_node.py for building and validating Blender scripts.
- Add docs.py for building and previewing documentation with Mike or MkDocs.
- Introduce model_exports.py for exporting PyTorch models to ONNX format.
- Develop pack.py for packaging the project with dependencies for different platforms.
- Add test_sync_models.py to validate sync_models functionality.
- Add test_tool_commands.py to ensure repository tools have correct command scripts.
- Initialize tools package with __init__.py.

src/anyimage/menu.py

@@ -1,6 +1,6 @@
 import bpy
 
-from .operators.common.image_data import is_image_empty
+from .common.image_data import is_image_empty
 from .operators.upscale import upscale_output_size