Add citation

CITATION.cff

@@ -0,0 +1,8 @@
+cff-version: 1.2.0
+message: "If you use this software, please cite it as below."
+authors:
+  - name: "MMDetection3D Contributors"
+title: "OpenMMLab's Next-generation Platform for General 3D Object Detection"
+date-released: 2020-07-23
+url: "https://github.com/open-mmlab/mmdetection3d"
+license: Apache-2.0

setup.py

@@ -196,7 +196,7 @@ def add_mim_extention():
                      'for general 3D object detection.'),
         long_description=readme(),
         long_description_content_type='text/markdown',
-        author='OpenMMLab',
+        author='MMDetection3D Contributors',
         author_email='[email protected]',
         keywords='computer vision, 3D object detection',
         url='https://github.com/open-mmlab/mmdetection3d',