Add namespace

Author: nidegen

android/build.gradle

@@ -22,6 +22,7 @@ rootProject.allprojects {
 apply plugin: 'com.android.library'
 
 android {
+    namespace "flutter.plugins.contactsservice.contactsservice"
     compileSdkVersion 30
 
     defaultConfig {

example/android/app/build.gradle

@@ -47,4 +47,4 @@ flutter {
 dependencies {
     androidTestImplementation 'androidx.test:runner:1.1.0'
     androidTestImplementation 'androidx.test:rules:1.1.0'
-}
+}