Update README.md

Author: pfitzseb

README.md

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 | Build | Coverage | Docs |
 |-------|----------|------|
-| [![Build Status](https://travis-ci.org/JuliaGizmos/WebIO.jl.svg?branch=master)](https://travis-ci.org/JuliaGizmos/WebIO.jl) | [![codecov](https://codecov.io/gh/JuliaGizmos/WebIO.jl/branch/master/graph/badge.svg)](https://codecov.io/gh/JuliaGizmos/WebIO.jl) | [![][docs-img]][docs-url]
+| [![CI](https://github.com/JuliaGizmos/WebIO.jl/actions/workflows/tests.yml/badge.svg)](https://github.com/JuliaGizmos/WebIO.jl/actions/workflows/tests.yml) | [![codecov](https://codecov.io/gh/JuliaGizmos/WebIO.jl/branch/master/graph/badge.svg)](https://codecov.io/gh/JuliaGizmos/WebIO.jl) | [![][docs-img]][docs-url]
 
 WebIO provides a simple abstraction for displaying and interacting with web content. It works with: