Create GitHub Actions workflow: build

.github/workflows/build.yml

@@ -0,0 +1,26 @@
+name: build
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Set up JDK 17
+      uses: actions/setup-java@v2
+      with:
+        java-version: '17'
+        distribution: 'temurin'
+
+    - name: Build with Gradle
+      uses: gradle/gradle-build-action@v2
+      with:
+        arguments: build