Removed Appveyor CI

.github/workflows/cmake.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-20.04, macos-latest, windows-latest]
+        os: [ubuntu-20.04, macos-latest, windows-latest, windows-2019]
 
     steps:
     - uses: actions/checkout@v2

README.md

@@ -2,7 +2,6 @@ cpp-peglib
 ==========
 
 [![](https://github.com/yhirose/cpp-peglib/workflows/CMake/badge.svg)](https://github.com/yhirose/cpp-peglib/actions)
-[![Build Status](https://ci.appveyor.com/api/projects/status/github/yhirose/cpp-peglib?branch=master&svg=true)](https://ci.appveyor.com/project/yhirose/cpp-peglib)
 
 C++17 header-only [PEG](http://en.wikipedia.org/wiki/Parsing_expression_grammar) (Parsing Expression Grammars) library. You can start using it right away just by including `peglib.h` in your project.