update readme badges

[veenstrajelmer]

What is the need for this task.
Since the code coverage is now computed by sonarcloud, it might be nice to communicate about this. And why not also adding the #downloads badge immediately.
Furthermore, the pypi badge in the readme is not the original link but "fury" that is lowres and updates only every once in a while. It should be

What is the task?
This is often done via a button in the README.md. This can be achieved by copying this markdown code:

[![PyPI version](https://img.shields.io/pypi/v/meshkernel.svg)](https://pypi.python.org/pypi/meshkernel)
[![Coverage](https://sonarcloud.io/api/project_badges/measure?project=Deltares_MeshKernelPy&metric=coverage)](https://sonarcloud.io/summary/overall?id=Deltares_MeshKernelPy)
[![Downloads](https://img.shields.io/pypi/dm/meshkernel.svg)](https://pypistats.org/packages/meshkernel)

It will look (and work) like this: