README: add GHA badge, remove Travis badge, remove AV badge

Author: DilumAluthge

README.md

@@ -3,8 +3,7 @@ LibCURL.jl
 
 *Julia wrapper for libCURL*
 
-[![Build Status](https://travis-ci.com/JuliaWeb/LibCURL.jl.svg?branch=master)](https://travis-ci.com/JuliaWeb/LibCURL.jl)
-[![Appveyor](https://ci.appveyor.com/api/projects/status/github/JuliaWeb/LibCurl.jl?svg=true)](https://ci.appveyor.com/project/shashi/libcurl-jl)
+[![CI](https://github.com/JuliaWeb/LibCURL.jl/actions/workflows/ci.yml/badge.svg)](https://github.com/JuliaWeb/LibCURL.jl/actions/workflows/ci.yml)
 [![codecov.io](http://codecov.io/github/JuliaWeb/LibCURL.jl/coverage.svg?branch=master)](http://codecov.io/github/JuliaWeb/LibCURL.jl?branch=master)
 
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