Set up basic GHA workflow

Signed-off-by: Frank Lichtenheld <frank@lichtenheld.com>

.github/workflows/build.yml

@@ -0,0 +1,18 @@
+name: Build
+
+on:
+  push:
+  pull_request:
+    branches: [ "master" ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v3
+    - name: Install dependencies
+      run: sudo apt-get update && sudo apt-get install mono-devel
+    - name: Build
+      run: ./build.sh