Add GitHub CI workflow to run tests

.github/workflows/ci.yml

@@ -0,0 +1,23 @@
+name: Continuous integration
+
+on: [push, pull_request]
+
+jobs:
+  linux:
+    name: CI
+    runs-on: ubuntu-20.04
+    timeout-minutes: 60
+    steps:
+      - name: Download repository
+        uses: actions/checkout@v4
+        with:
+          submodules: recursive
+
+      - name: Generate Makefile
+        run: cmake -S . -B build/ -G "Unix Makefiles" 
+
+      - name: Build
+        run: cmake --build build/ -j 2
+
+      - name: Run tests
+        run: ./build/tests