Add GH action runner for testing (#232)

* Add GH action runner

* Install autotools etc

* Add matrix for libidn, libidn2, libicu

.github/workflows/unit-tests.yml

@@ -0,0 +1,27 @@
+name: libpsl
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: ["**"]
+
+jobs:
+  test:
+    name: Test
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: true
+      max-parallel: 3
+      matrix:
+        runtime: ["libidn", "libidn2", "libicu"]
+    steps:
+    - name: Check out
+      uses: actions/checkout@v4
+    - name: Install dependencies
+      run: sudo apt-get install -y autopoint autoconf automake gtk-doc-tools libidn2-dev libunistring-dev libicu-dev libidn-dev
+    - name: Test with ${{matrix.runtime}}
+      run: |
+          ./autogen.sh
+          CFLAGS="-O0 -Wall -Wextra" ./configure --enable-runtime=${{matrix.runtime}}
+          make check