Remove Appveyor CI [ci skip]

Author: martinmoene

README.md

@@ -1,6 +1,6 @@
 # variant lite: A single-file header-only version of a C++17-like variant, a type-safe union for C++98, C++11 and later
 
-[![Language](https://img.shields.io/badge/C%2B%2B-98/11/14/17-blue.svg)](https://en.wikipedia.org/wiki/C%2B%2B#Standardization) [![License](https://img.shields.io/badge/license-BSL-blue.svg)](https://opensource.org/licenses/BSL-1.0) [![Build Status](https://github.com/martinmoene/variant-lite/actions/workflows/ci.yml/badge.svg)](https://github.com/martinmoene/variant-lite/actions/workflows/ci.yml) [![Build status](https://ci.appveyor.com/api/projects/status/w2dgn3fxyrd6vcq8?svg=true)](https://ci.appveyor.com/project/martinmoene/variant-lite) [![Version](https://badge.fury.io/gh/martinmoene%2Fvariant-lite.svg)](https://github.com/martinmoene/variant-lite/releases) [![Latest download](https://img.shields.io/badge/latest-download-blue.svg)](https://raw.githubusercontent.com/martinmoene/variant-lite/master/include/nonstd/variant.hpp) [![Conan](https://img.shields.io/badge/on-conan-blue.svg)](https://conan.io/center/variant-lite) [![Vcpkg](https://img.shields.io/badge/on-vcpkg-blue.svg)](https://vcpkg.link/ports/variant-lite) [![Try it online](https://img.shields.io/badge/on-wandbox-blue.svg)](https://wandbox.org/permlink/tpG9nmapo2mUKUCo) [![Try it on godbolt online](https://img.shields.io/badge/on-godbolt-blue.svg)](https://godbolt.org/z/WY7HhQ)
+[![Language](https://img.shields.io/badge/C%2B%2B-98/11/14/17-blue.svg)](https://en.wikipedia.org/wiki/C%2B%2B#Standardization) [![License](https://img.shields.io/badge/license-BSL-blue.svg)](https://opensource.org/licenses/BSL-1.0) [![Build Status](https://github.com/martinmoene/variant-lite/actions/workflows/ci.yml/badge.svg)](https://github.com/martinmoene/variant-lite/actions/workflows/ci.yml) [![Version](https://badge.fury.io/gh/martinmoene%2Fvariant-lite.svg)](https://github.com/martinmoene/variant-lite/releases) [![Latest download](https://img.shields.io/badge/latest-download-blue.svg)](https://raw.githubusercontent.com/martinmoene/variant-lite/master/include/nonstd/variant.hpp) [![Conan](https://img.shields.io/badge/on-conan-blue.svg)](https://conan.io/center/variant-lite) [![Vcpkg](https://img.shields.io/badge/on-vcpkg-blue.svg)](https://vcpkg.link/ports/variant-lite) [![Try it online](https://img.shields.io/badge/on-wandbox-blue.svg)](https://wandbox.org/permlink/tpG9nmapo2mUKUCo) [![Try it on godbolt online](https://img.shields.io/badge/on-godbolt-blue.svg)](https://godbolt.org/z/WY7HhQ)
 
 **Contents**  
 - [Example usage](#example-usage)