Add Build workflow

.github/workflows/build.yml

@@ -0,0 +1,18 @@
+name: Build
+
+on:
+  push:
+  workflow_dispatch: # allow manual trigger
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - uses: actions/setup-java@v3
+        with:
+          distribution: 'adopt'
+          java-version: '18'
+
+      - run: ./gradlew --stacktrace check