Remove AppVeyor badge and workflow (nonstd-lite issue 79) [ci skip]

Author: martinmoene

README.md

@@ -2,7 +2,7 @@
 
 A work in its infancy. Suggested and contributed to by Peter Featherstone.
 
-[![Language](https://img.shields.io/badge/C%2B%2B-11/14/17/20-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/invoke-lite/actions/workflows/ci.yml/badge.svg)](https://github.com/martinmoene/invoke-lite/actions/workflows/ci.yml) [![Build status](https://ci.appveyor.com/api/projects/status/nrnbfhvvp39ex075?svg=true)](https://ci.appveyor.com/project/martinmoene/invoke-lite) [![Version](https://badge.fury.io/gh/martinmoene%2Finvoke-lite.svg)](https://github.com/martinmoene/invoke-lite/releases) [![download](https://img.shields.io/badge/latest-download-blue.svg)](https://raw.githubusercontent.com/martinmoene/invoke-lite/master/include/nonstd/invoke.hpp) [![Conan](https://img.shields.io/badge/on-conan-blue.svg)]() [![Try it online](https://img.shields.io/badge/on-wandbox-blue.svg)](https://wandbox.org/permlink/cs8Qw9RsGXpuzl8m) [![Try it on godbolt online](https://img.shields.io/badge/on-godbolt-blue.svg)](https://godbolt.org/z/q7W7PWxGr)
+[![Language](https://img.shields.io/badge/C%2B%2B-11/14/17/20-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/invoke-lite/actions/workflows/ci.yml/badge.svg)](https://github.com/martinmoene/invoke-lite/actions/workflows/ci.yml) [![Version](https://badge.fury.io/gh/martinmoene%2Finvoke-lite.svg)](https://github.com/martinmoene/invoke-lite/releases) [![download](https://img.shields.io/badge/latest-download-blue.svg)](https://raw.githubusercontent.com/martinmoene/invoke-lite/master/include/nonstd/invoke.hpp) [![Conan](https://img.shields.io/badge/on-conan-blue.svg)]() [![Try it online](https://img.shields.io/badge/on-wandbox-blue.svg)](https://wandbox.org/permlink/cs8Qw9RsGXpuzl8m) [![Try it on godbolt online](https://img.shields.io/badge/on-godbolt-blue.svg)](https://godbolt.org/z/q7W7PWxGr)
 
 **Contents**