Add gradle build workflow

.github/workflows/gradle.yml

@@ -0,0 +1,32 @@
+name: Build with Gradle
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+  workflow_dispatch:
+
+concurrency:
+  group: build-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  gradle:
+    strategy:
+      matrix:
+        os: [ubuntu-latest]
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-java@v3
+        with:
+          distribution: temurin
+          java-version: 11
+
+      - name: Setup Gradle
+        uses: gradle/gradle-build-action@v2
+        with:
+          gradle-version: 7.4 # https://github.com/runelite/plugin-hub/blob/master/package/gradle/wrapper/gradle-wrapper.properties
+
+      - name: Execute Gradle build
+        run: gradle build