Update CI badge

Author: timholy

README.md

@@ -1,6 +1,5 @@
 # ImagineInterface
-[![Build Status](https://travis-ci.com/HolyLab/ImagineInterface.jl.svg?branch=master)](https://travis-ci.org/HolyLab/ImagineInterface)
-[![Build status](https://ci.appveyor.com/api/projects/status/obywii010u9stx5f/branch/master?svg=true)](https://ci.appveyor.com/project/Cody-G/imagineinterface/branch/master)
+[![CI](https://github.com/HolyLab/ImagineInterface.jl/actions/workflows/CI.yml/badge.svg)](https://github.com/HolyLab/ImagineInterface.jl/actions/workflows/CI.yml)
 [![codecov](https://codecov.io/gh/HolyLab/ImagineInterface.jl/branch/master/graph/badge.svg)](https://codecov.io/gh/HolyLab/ImagineInterface.jl)
 
 **Note:** Julia 0.6 users should checkout the `julia0.6` branch; `master` works on Julia 0.7/1.x only.