Add ci flakiness score to readme
<a href="http://libp2p.io/"><img src="https://img.shields.io/badge/project-libp2p-yellow.svg?style=flat-square" /></a>
<a href="https://pkg.go.dev/github.com/libp2p/go-libp2p"><img src="https://pkg.go.dev/badge/github.com/libp2p/go-libp2p.svg" alt="Go Reference"></a>
<a href="https://discuss.libp2p.io"><img src="https://img.shields.io/discourse/https/discuss.libp2p.io/posts.svg"/></a>
+ <a href="https://marcopolo.github.io/FlakyTests/"><img src="https://marcopolo.github.io/FlakyTests/current-score.svg"/></a>
</p>
# Table of Contents
