Add CI that builds source and runs unit tests

.github/workflows/CI.yml

@@ -0,0 +1,37 @@
+name: CI
+
+on: [push, pull_request]
+
+jobs:
+  Build:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [macos-14, ubuntu-24.04]
+
+    env:
+      PREFIX: install
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v1
+
+    - uses: fortran-lang/setup-fpm@v4
+      with:
+        github-token: ${{ secrets.GITHUB_TOKEN }}
+
+    - name: Install on Ubuntu
+      if: contains(matrix.os, 'ubuntu')
+      run: |
+        sudo apt update
+        sudo apt install -y gfortran-14 g++-14
+        fpm build
+
+    - name: Install on macOS
+      if: contains(matrix.os, 'macos')
+      run: |
+        fpm build
+
+    - name: Run unit tests
+      run: |
+        fpm test