Internationalization (#131)

Replaced hardcoded English strings with locale-based variables based on the [easy_localization](https://pub.dev/packages/easy_localization) Flutter plugin.

lib/main.dart

@@ -15,6 +15,7 @@ import 'package:provider/provider.dart';
 import 'package:dynamic_color/dynamic_color.dart';
 import 'package:device_info_plus/device_info_plus.dart';
 import 'package:android_alarm_manager_plus/android_alarm_manager_plus.dart';
+import 'package:easy_localization/easy_localization.dart';
 
 const String currentVersion = '0.8.1';
 const String currentReleaseTag =
@@ -25,14 +26,14 @@ const int bgUpdateCheckAlarmId = 666;
 @pragma('vm:entry-point')
 Future<void> bgUpdateCheck(int taskId, Map<String, dynamic>? params) async {
   LogsProvider logs = LogsProvider();
-  logs.add('Started BG update check task');
+  logs.add(tr('startedBgUpdateTask'));
   int? ignoreAfterMicroseconds = params?['ignoreAfterMicroseconds'];
   WidgetsFlutterBinding.ensureInitialized();
   await AndroidAlarmManager.initialize();
   DateTime? ignoreAfter = ignoreAfterMicroseconds != null
       ? DateTime.fromMicrosecondsSinceEpoch(ignoreAfterMicroseconds)
       : null;
-  logs.add('Bg update ignoreAfter is $ignoreAfter');
+  logs.add(tr('bgUpdateIgnoreAfterIs', args: [ignoreAfter.toString()]));
   var notificationsProvider = NotificationsProvider();
   await notificationsProvider.notify(checkingUpdatesNotification);
   try {
@@ -44,14 +45,14 @@ Future<void> bgUpdateCheck(int taskId, Map<String, dynamic>? params) async {
     DateTime nextIgnoreAfter = DateTime.now();
     String? err;
     try {
-      logs.add('Started actual BG update checking');
+      logs.add(tr('startedActualBGUpdateCheck'));
       await appsProvider.checkUpdates(
           ignoreAppsCheckedAfter: ignoreAfter, throwErrorsForRetry: true);
     } catch (e) {
       if (e is RateLimitError || e is SocketException) {
         var remainingMinutes = e is RateLimitError ? e.remainingMinutes : 15;
-        logs.add(
-            'BG update checking encountered a ${e.runtimeType}, will schedule a retry check in $remainingMinutes minutes');
+        logs.add(plural('bgUpdateGotErrorRetryInMinutes', remainingMinutes,
+            args: [e.runtimeType.toString()]));
         AndroidAlarmManager.oneShot(Duration(minutes: remainingMinutes),
             Random().nextInt(pow(2, 31) as int), bgUpdateCheck, params: {
           'ignoreAfterMicroseconds': nextIgnoreAfter.microsecondsSinceEpoch
@@ -80,7 +81,7 @@ Future<void> bgUpdateCheck(int taskId, Map<String, dynamic>? params) async {
     //       cancelExisting: true);
     // }
     logs.add(
-        'BG update checking found ${newUpdates.length} updates - will notify user if needed');
+        plural('bgCheckFoundUpdatesWillNotifyIfNeeded', newUpdates.length));
     if (newUpdates.isNotEmpty) {
       notificationsProvider.notify(UpdateNotification(newUpdates));
     }
@@ -91,13 +92,14 @@ Future<void> bgUpdateCheck(int taskId, Map<String, dynamic>? params) async {
     notificationsProvider
         .notify(ErrorCheckingUpdatesNotification(e.toString()));
   } finally {
-    logs.add('Finished BG update check task');
+    logs.add(tr('bgUpdateTaskFinished'));
     await notificationsProvider.cancel(checkingUpdatesNotification.id);
   }
 }
 
 void main() async {
   WidgetsFlutterBinding.ensureInitialized();
+  await EasyLocalization.ensureInitialized();
   if ((await DeviceInfoPlugin().androidInfo).version.sdkInt >= 29) {
     SystemChrome.setSystemUIOverlayStyle(
       const SystemUiOverlayStyle(systemNavigationBarColor: Colors.transparent),
@@ -112,7 +114,11 @@ void main() async {
       Provider(create: (context) => NotificationsProvider()),
       Provider(create: (context) => LogsProvider())
     ],
-    child: const Obtainium(),
+    child: EasyLocalization(
+        supportedLocales: const [Locale('en')],
+        path: 'assets/translations',
+        fallbackLocale: const Locale('en'),
+        child: const Obtainium()),
   ));
 }
 
@@ -139,7 +145,7 @@ class _ObtainiumState extends State<Obtainium> {
     } else {
       bool isFirstRun = settingsProvider.checkAndFlipFirstRun();
       if (isFirstRun) {
-        logs.add('This is the first ever run of Obtainium');
+        logs.add(tr('firstRun'));
         // If this is the first run, ask for notification permissions and add Obtainium to the Apps list
         Permission.notification.request();
         appsProvider.saveApps([
@@ -161,8 +167,8 @@ class _ObtainiumState extends State<Obtainium> {
       // Register the background update task according to the user's setting
       if (existingUpdateInterval != settingsProvider.updateInterval) {
         if (existingUpdateInterval != -1) {
-          logs.add(
-              'Setting update interval to ${settingsProvider.updateInterval}');
+          logs.add(tr('settingUpdateCheckIntervalTo',
+              args: [settingsProvider.updateInterval.toString()]));
         }
         existingUpdateInterval = settingsProvider.updateInterval;
         if (existingUpdateInterval == 0) {
@@ -195,6 +201,9 @@ class _ObtainiumState extends State<Obtainium> {
       }
       return MaterialApp(
           title: 'Obtainium',
+          localizationsDelegates: context.localizationDelegates,
+          supportedLocales: context.supportedLocales,
+          locale: context.locale,
           theme: ThemeData(
               useMaterial3: true,
               colorScheme: settingsProvider.theme == ThemeSettings.dark