Add build workflow.

.github/workflows/cmake-build.yml

@@ -0,0 +1,31 @@
+name: CMake Build
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+
+jobs:
+  build:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+
+      - name: Set up CMake
+        uses: jwlawson/actions-setup-cmake@v1
+        with:
+          cmake-version: '3.21.2'
+
+      - name: Configure CMake
+        run: cmake . -B build
+
+      - name: Build with CMake
+        run: cmake --build build --config Release
+
+