Add unit test workflow

.github/workflows/utests.yml

@@ -0,0 +1,38 @@
+name: Unit tests
+
+on:
+  push:
+    branches: '*'
+  pull_request:
+    branches: [ "master" ]
+
+env:
+  BUILD_TYPE: Debug
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v3
+      with:
+        submodules: 'recursive'
+
+    - name: Install dependencies
+      run: |
+        sudo apt-get update
+        sudo apt-get install -y nlohmann-json3-dev libutfcpp-dev libgd-dev
+      shell: bash
+    - name: Install Qt
+      uses: jurplel/install-qt-action@v3
+      with:
+        version: '6.6.*'
+    - name: Configure CMake
+      run: cmake -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} -DSCRATCHCPPGUI_BUILD_UNIT_TESTS=ON
+
+    - name: Build
+      run: cmake --build ${{github.workspace}}/build --config ${{env.BUILD_TYPE}} -j$(nproc --all)
+
+    - name: Run unit tests
+      run: ctest --test-dir build -V
+