ci: cache gradle build

Author: Maximilian Häming

.github/workflows/main.yml

@@ -16,7 +16,9 @@ jobs:
       - name: Setup JDK
         uses: actions/setup-java@v3.13.0
         with:
-          java-version: 1.8
+          java-version: '11'
+          distribution: 'temurin'
+          cache: gradle
       - name: Build with Gradle
         run: ./gradlew build
       - name: Upload APK