ci: add build test workflow

Author: tksimeji

.github/workflows/build.yml

@@ -0,0 +1,40 @@
+name: Build
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  build:
+    name: Build with Java 21
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+    env:
+      VERSION: 0.0.0-SNAPSHOT
+
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+      - uses: actions/setup-java@be666c2fcd27ec809703dec50e508c2fdc7f6654 # v5.2.0
+        with:
+          distribution: "adopt"
+          java-version: 21
+
+      - name: Setup Gradle
+        uses: gradle/actions/setup-gradle@f29f5a9d7b09a7c6b29859002d29d24e1674c884 # v5.0.1
+
+      - name: Build with Gradle
+        run: ./gradlew build
+
+      - name: Upload a Build Artifact
+        uses: actions/upload-artifact@b7c566a772e6b6bfb58ed0dc250532a479d7789f # v6.0.0
+        with:
+          path: modules/**/build/libs/*.jar