Modify long description format of whl package

Signed-off-by: Nzhoufeng <zhoufeng54@huawei.com>

setup.py

@@ -161,6 +161,7 @@ setup(
     description='MindSpore is a new open source deep learning training/inference '
     'framework that could be used for mobile, edge and cloud scenarios.',
     long_description="\n\n".join([readme, release]),
+    long_description_content_type="text/markdown",
     packages=find_packages(),
     package_data=package_data,
     include_package_data=True,