add coverage, PyPI badges
[![License](https://img.shields.io/badge/license-Apache%202.0-green.svg)](https://opensource.org/licenses/Apache-2.0)
[![CI Build](https://github.com/Project-MONAI/MONAI/workflows/build/badge.svg?branch=master)](https://github.com/Project-MONAI/MONAI/commits/master)
[![Documentation Status](https://readthedocs.org/projects/monai/badge/?version=latest)](https://monai.readthedocs.io/en/latest/?badge=latest)
+[![codecov](https://codecov.io/gh/Project-MONAI/MONAI/branch/master/graph/badge.svg)](https://codecov.io/gh/Project-MONAI/MONAI)
+[![PyPI version](https://badge.fury.io/py/monai.svg)](https://badge.fury.io/py/monai)
MONAI is a [PyTorch](https://pytorch.org/)-based, [open-source](https://github.com/Project-MONAI/MONAI/blob/master/LICENSE) platform for deep learning in healthcare imaging. Its ambitions are:
- developing a community of academic, industrial and clinical researchers collaborating on a common foundation;
