Added actions to build prs and upload artifacts

.github/workflows/pull_requests.yml

@@ -0,0 +1,31 @@
+name: 'Build master'
+
+on:
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - name: Set up JDK 1.8
+        uses: actions/setup-java@v1
+        with:
+          java-version: 1.8
+      - name: Grant execute permission for gradlew
+        run: chmod +x gradlew
+      - name: Use gradle cache for faster builds
+        uses: actions/cache@v1
+        with:
+          path: ~/.gradle/caches
+          key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle') }}
+      - name: Build with Gradle
+        run: |
+          echo "::set-env name=PR_NUMBER::$(jq --raw-output .pull_request.number "$GITHUB_EVENT_PATH")"
+          ./gradlew build
+      - uses: actions/upload-artifact@v2
+        with:
+          name: jar-artifacts
+          path: build/libs/appliedenergistics2-?.?.?+pr.*[0-9].jar