fix(flutter_vibrate): use flutter.compileSdkVersion

The hardcoded `compileSdkVersion` was causing build failures for users who did not have the exact Android SDK version installed.

This change updates the `build.gradle` file to use `flutter.compileSdkVersion`, which is the standard and recommended approach for Flutter plugins. This makes the plugin adapt to the `compileSdkVersion` defined by the consuming Flutter application, resolving the build error and making the package more robust against future Flutter SDK updates.

packages/flutter_vibrate/android/build.gradle

@@ -20,10 +20,14 @@ rootProject.allprojects {
 }
 
 apply plugin: 'com.android.library'
+apply plugin: 'dev.flutter.flutter-gradle-plugin'
+apply plugin: 'dev.flutter.flutter-gradle-plugin'
+apply plugin: 'dev.flutter.flutter-gradle-plugin'
+apply plugin: 'dev.flutter.flutter-gradle-plugin'
 
 android {
     namespace "flutter.plugins.vibrate"
-    compileSdkVersion 30
+    compileSdkVersion flutter.compileSdkVersion
 
     defaultConfig {
         minSdkVersion 16