👷 add more GitHub actions workflows

.github/workflows/macos.yml

+name: Windows
+
+on: [push]
+
+jobs:
+  build:
+
+    runs-on: windows-latest
+
+    steps:
+    - uses: actions/checkout@v1
+    - name: prepare
+      run: mkdir build
+    - name: cmake
+      run: cd build ; cmake ..
+    - name: build
+      run: make -C build
+    - name: test
+      run: cd build ; ctest -j 10

.github/workflows/ccpp.yml → .github/workflows/ubuntu.yml

-name: C/C++ CI
+name: Ubuntu
 
 on: [push]
 
@@ -6,7 +6,7 @@ jobs:
   build:
 
     runs-on: ubuntu-latest
-    
+
     steps:
     - uses: actions/checkout@v1
     - name: prepare

.github/workflows/windows.yml

+name: macOS
+
+on: [push]
+
+jobs:
+  build:
+
+    runs-on: macos-latest
+
+    steps:
+    - uses: actions/checkout@v1
+    - name: prepare
+      run: mkdir build
+    - name: cmake
+      run: cd build ; cmake ..
+    - name: build
+      run: make -C build
+    - name: test
+      run: cd build ; ctest -j 10