chore: add code style check to dev branch pushes

.github/workflows/testing.yml

@@ -10,6 +10,35 @@ concurrency:
   cancel-in-progress: true
 
 jobs:
+  style:
+    name: Code style check
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v3
+
+      - uses: actions/cache@v3
+        with:
+          path: |
+            ~/.gradle/caches
+            ~/.gradle/wrapper
+          key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle*', '**/gradle-wrapper.properties') }}
+          restore-keys: |
+            ${{ runner.os }}-gradle-
+
+      - name: set up JDK 17
+        uses: actions/setup-java@v3
+        with:
+          distribution: 'oracle'
+          java-version: 17
+          cache: 'gradle'
+
+      - name: Setup Android SDK
+        uses: android-actions/setup-android@v2
+
+      - name: Ktlint check
+        run: ./gradlew ktlintCheck
+
   apk:
     name: Generate and upload APK to Discord
     runs-on: ubuntu-latest