Add a Financial Contributors badge.
# ION
ION is a distributed RTC system written by pure go and flutter
-[![Build Status](https://travis-ci.com/pion/ion.svg?branch=master)](https://travis-ci.com/pion/ion)
+[![Financial Contributors on Open Collective](https://opencollective.com/pion-ion/all/badge.svg?label=financial+contributors)](https://opencollective.com/pion-ion) [![Build Status](https://travis-ci.com/pion/ion.svg?branch=master)](https://travis-ci.com/pion/ion)
![MIT](https://img.shields.io/badge/License-MIT-yellow.svg)
[![slack](https://img.shields.io/badge/join-us%20on%20slack-gray.svg?longCache=true&logo=slack&colorB=brightgreen)](https://pion.ly/slack)
[![Go Report Card](https://goreportcard.com/badge/github.com/pion/ion)](https://goreportcard.com/report/github.com/pion/ion)
