Added actions to test the new C++ code.

.github/workflows/check-install.yaml

@@ -0,0 +1,42 @@
+on:
+  push:
+    branches:
+      - master
+    paths-ignore:
+      - README.md
+      - 'docs/**'
+  pull_request:
+    paths-ignore:
+      - README.md
+      - 'docs/**'
+
+name: Check CMake install
+
+jobs:
+  install:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Get latest CMake
+      uses: lukka/get-cmake@latest
+
+    - name: Configure the build
+      run: cmake -S . -B build -DGESEL_TESTS=OFF
+
+    - name: Install the library
+      run: sudo cmake --install build
+
+    - name: Test downstream usage
+      run: |
+        mkdir _downstream
+        touch _downstream/source.cpp
+        cat << EOF > _downstream/CMakeLists.txt
+        cmake_minimum_required(VERSION 3.24)
+        project(test_install)
+        add_executable(whee source.cpp)
+        find_package(gesel_gesel)
+        target_link_libraries(whee gesel::gesel)
+        EOF
+        cd _downstream && cmake -S . -B build

.github/workflows/run-tests.yaml

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+on:
+  push:
+    branches:
+      - master
+    paths-ignore:
+      - README.md
+      - 'docs/**'
+  pull_request:
+    paths-ignore:
+      - README.md
+      - 'docs/**'
+
+name: Run unit tests
+
+jobs:
+  test:
+    name: ${{ matrix.config.name }}
+    runs-on: ${{ matrix.config.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        config:
+        - {
+            name: "Ubuntu Latest GCC, coverage enabled", 
+            os: ubuntu-latest,
+            cov: true
+          }
+        - {
+            name: "macOS Latest Clang", 
+            os: macos-latest
+          }
+
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Get latest CMake
+      uses: lukka/get-cmake@latest
+
+    - name: Configure the build for Mac
+      if: ${{ matrix.config.os == 'macos-latest' }}
+      run: |
+        cmake -S . -B build
+
+    - name: Configure the build with coverage and HDF5
+      if: ${{ matrix.config.os == 'ubuntu-latest' }}
+      run: |
+        cmake -S . -B build -DCODE_COVERAGE=ON
+
+    - name: Run the build
+      run: cmake --build build
+
+    - name: Run the tests
+      run: |
+        cd build
+        ctest
+
+    - name: Generate code coverage
+      if: ${{ matrix.config.cov }}
+      run: |
+        cd build/tests/CMakeFiles/
+        find -type f -name "*.gcno" -execdir gcov -abcfu {} +
+
+    - name: Upload to Codecov
+      if: ${{ matrix.config.cov }}
+      uses: codecov/codecov-action@v5
+      with:
+        directory: build/tests/CMakeFiles/
+      env:
+        CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}