Add sonar plugin and github actions file for sonar analysis

Copied from sonarcloud.io setup page with minor adjustments. Adjusted branch to 'dev' and updated versions

.github/workflows/ci.yml

@@ -40,3 +40,34 @@ jobs:
         with:
           name: app
           path: app/build/outputs/apk/debug/*.apk
+  sonar:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0  # Shallow clones should be disabled for a better relevancy of analysis
+
+      - name: Set up JDK 11
+        uses: actions/setup-java@v1.4.3
+        with:
+          java-version: 11 # Sonar requires JDK 11
+
+      - name: Cache SonarCloud packages
+        uses: actions/cache@v2
+        with:
+          path: ~/.sonar/cache
+          key: ${{ runner.os }}-sonar
+          restore-keys: ${{ runner.os }}-sonar
+
+      - name: Cache Gradle packages
+        uses: actions/cache@v2
+        with:
+          path: ~/.gradle/caches
+          key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle') }}
+          restore-keys: ${{ runner.os }}-gradle
+
+      - name: Build and analyze
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}  # Needed to get PR information, if any
+          SONAR_TOKEN: ${{ secrets.SONAR_TOKEN }}
+        run: ./gradlew build sonarqube --info