feat: Add VRM Blender addon with complete import/export functionality

- Add core VRM addon infrastructure with manifest and registration
- Add common utilities module with file system, logging, and conversion helpers
- Add human bone mapper with support for multiple rigging standards (Mixamo, MMD, Unreal, Rigify, etc.)
- Add VRM 0.x and 1.x format support with property groups and handlers
- Add editor UI panels for VRM metadata, spring bones, and MToon materials
- Add exporter with glTF2 extension support for VRM format serialization
- Add importer with scene reconstruction and armature generation
- Add MToon shader support with auto-setup and material migration
- Add spring bone physics simulation with constraint handling
- Add node constraint editor for advanced rigging control
- Add comprehensive validation and error handling with user dialogs
- Add scene watcher for real-time property synchronization
- Add workspace management and preference system
- Include Python cache files and Blender manifest configuration
- This is the initial commit establishing the complete VRM addon ecosystem for Blender

__init__.py

@@ -0,0 +1,41 @@
+# SPDX-License-Identifier: MIT OR GPL-3.0-or-later
+# SPDX-FileCopyrightText: 2018 iCyP
+
+from . import registration
+from .exporter import gltf2_export_user_extension
+from .importer import gltf2_import_user_extension
+
+bl_info = {
+    "name": "VRM format",
+    "author": "saturday06, iCyP",
+    "version": (
+        3,  # x-release-please-major
+        17,  # x-release-please-minor
+        1,  # x-release-please-patch
+    ),
+    "location": "File > Import-Export",
+    "description": "Import-Edit-Export VRM",
+    "blender": (2, 93, 0),
+    "warning": "",
+    "support": "COMMUNITY",
+    "wiki_url": "",
+    "doc_url": "https://vrm-addon-for-blender.info",
+    "tracker_url": "https://github.com/saturday06/VRM-Addon-for-Blender/issues",
+    "category": "Import-Export",
+}
+
+
+def register() -> None:
+    registration.register()
+
+
+def unregister() -> None:
+    registration.unregister()
+
+
+class glTF2ImportUserExtension(gltf2_import_user_extension.glTF2ImportUserExtension):
+    pass
+
+
+class glTF2ExportUserExtension(gltf2_export_user_extension.glTF2ExportUserExtension):
+    pass