ci: add build CI (with artifacts)

Author: iLynxcat

.github/workflows/build.yml

@@ -0,0 +1,41 @@
+name: Build
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+# Cancel in-progress builds
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Validate Gradle wrapper
+        uses: gradle/actions/wrapper-validation@v3
+
+      - name: Set up JDK (Temurin 21)
+        uses: actions/setup-java@v4
+        with:
+          distribution: "temurin"
+          java-version: "21"
+          cache: "gradle"
+
+      - name: Build with Gradle
+        run: ./gradlew build --no-daemon
+
+      - name: Upload build artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          name: plugin-${{ github.sha }}
+          path: build/libs/*.jar # Upload all generated jars
+          retention-days: 30
+          if-no-files-found: error