ci: add workflow for running tests on pull requests

Author: tronghn

.github/workflows/test-pull-requests.yml

@@ -0,0 +1,34 @@
+name: Test pull requests
+
+on: [pull_request]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout latest code
+        uses: actions/checkout@v2
+
+      - name: Set up JDK 11
+        uses: actions/setup-java@v1
+        with:
+          java-version: 11
+
+      - name: Setup build cache
+        uses: actions/cache@v1
+        with:
+          path: ~/.gradle/caches
+          key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle.kts') }}
+          restore-keys: |
+            ${{ runner.os }}-gradle-
+
+      - name: Setup Gradle wrapper cache
+        uses: actions/cache@v1
+        with:
+          path: ~/.gradle/wrapper
+          key: ${{ runner.os }}-gradle-wrapper-${{ hashFiles('gradle/wrapper/gradle-wrapper.properties') }}
+          restore-keys: |
+            ${{ runner.os }}-gradle-wrapper-
+
+      - name: Build with Gradle
+        run: ./gradlew clean build