switched from appveyor to github workflow

.github/workflows/check_build.yaml

@@ -0,0 +1,43 @@
+name: Check Builds
+
+on:
+  push:
+    paths:
+        - src/**
+        - main.c
+        - Makefile
+        - CMakeLists.txt
+        - .github/workflows/check-build.yaml
+
+jobs:
+  ubuntu-build:
+    runs-on: ubuntu-latest-4-cores
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          submodules: recursive
+      - name: CMake
+        run: cmake -S . -B build
+      - name: Build
+        run: cmake --build build
+      - name: Upload build artifact
+        uses: actions/upload-artifact@v2
+        with:
+          name: Cosmo-Ubuntu
+          path: bin
+
+  windows-build:
+    runs-on: windows-latest
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          submodules: recursive
+      - name: Create CMake build files
+        run: cmake -B build -DCMAKE_BUILD_TYPE=MinSizeRel
+      - name: Check compilation
+        run: cmake --build build --config MinSizeRel
+      - name: Upload build artifact
+        uses: actions/upload-artifact@v2
+        with:
+          name: Cosmo-Windows
+          path: winbin