Support targetSDK 31 (required from Play store)

- Components using IntentFilter must set android:exported="true"
- Other required was not impacted

android/app/build.gradle

@@ -41,7 +41,7 @@ android {
     defaultConfig {
         applicationId "com.linagora.android.teammail"
         minSdkVersion 16
-        targetSdkVersion 30
+        targetSdkVersion 31
         versionCode flutterVersionCode.toInteger()
         versionName flutterVersionName
         // The number of method references in a .dex file cannot exceed 64K
@@ -76,4 +76,5 @@ flutter {
 dependencies {
     implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
     implementation 'com.android.support:multidex:1.0.3'
+    implementation 'androidx.work:work-runtime-ktx:2.7.0'
 }

android/app/src/main/AndroidManifest.xml

@@ -37,6 +37,7 @@
         android:icon="@mipmap/ic_launcher">
         <activity
             android:name=".MainActivity"
+            android:exported="true"
             android:launchMode="singleTask"
             android:theme="@style/LaunchTheme"
             android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"