docs: add cover.run badge and visually tweak other badges

README.md

@@ -1,8 +1,9 @@
 # did
 
 [![Build Status](https://dev.azure.com/ockam-network/ockam-network-open-source/_apis/build/status/ockam-network.did)](https://dev.azure.com/ockam-network/ockam-network-open-source/_build/latest?definitionId=7)
-[![GoDoc](https://godoc.org/github.com/ockam-network/did?status.svg)](https://godoc.org/github.com/ockam-network/did)
-[![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](LICENSE)
+[![cover.run](https://cover.run/go/github.com/ockam-network/did.svg?tag=golang-1.10)](https://cover.run/go?tag=golang-1.10&repo=github.com%2Fockam-network%2Fdid)
+[![GoDoc](https://img.shields.io/badge/godoc-reference-blue.svg?style=flat-square)](https://godoc.org/github.com/ockam-network/did)
+[![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg?style=flat-square)](LICENSE)
 
 `did` is a Go package that provides tools to work with
 [Decentralized Identifiers (DIDs)](https://w3c-ccg.github.io/did-spec).