Initial commit: DCNv4 custom op mirror setup

- Add enhanced README with project structure and quick start guide
- Initialize repository with DCNv4 CUDA extension (PyTorch module)
- Include classification, detection, and segmentation subdirectories
- Reference upstream OpenGVLab DCNv4 implementation

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

detection/mmdet_custom/models/detectors/dino.py

@@ -0,0 +1,10 @@
+# Copyright (c) OpenMMLab. All rights reserved.
+from mmdet.models.builder import DETECTORS
+from mmdet.models.detectors.detr import DETR
+
+
+@DETECTORS.register_module()
+class DINO(DETR):
+    
+    def __init__(self, *args, **kwargs):
+        super(DETR, self).__init__(*args, **kwargs)