title: Can't release app or build web because of this package: blue_thermal_printer: ^1.1.9
body: <p>When I run this command</p>
  <pre><code>flutter run --release
  flutter build web --web-renderer html
  </code></pre>
  <p>I get this error in console:</p>
  <pre><code>Launching lib\main.dart on Infinix X656 in release mode...
  /C:/Users/Bilal%20Saeed/AppData/Local/Pub/Cache/hosted/pub.dartlang.org/blue_thermal_printer-1.1.9/lib/blue_thermal_printer.dart:34:28: Error: Type 'Registrar' not
   found.
    static void registerWith(Registrar registrar) {
                             ^^^^^^^^^
  /C:/Users/Bilal%20Saeed/AppData/Local/Pub/Cache/hosted/pub.dartlang.org/blue_thermal_printer-1.1.9/lib/blue_thermal_printer.dart:34:28: Error: 'Registrar' isn't a
  type.
    static void registerWith(Registrar registrar) {
                             ^^^^^^^^^
  /C:/Users/Bilal%20Saeed/AppData/Local/Pub/Cache/hosted/pub.dartlang.org/blue_thermal_printer-1.1.9/lib/blue_thermal_printer.dart:35:24: Error: Setter not found: 'i
  nstance'.
      BlueThermalPrinter.instance = BlueThermalPrinter._();
                         ^^^^^^^^
  
  
  FAILURE: Build failed with an exception.
  
  * Where:
  Script 'D:\All Data\Softwares\Latest Flutter\flutter\packages\flutter_tools\gradle\flutter.gradle' line: 1005
  
  * What went wrong:
  Execution failed for task ':app:compileFlutterBuildRelease'.
  &gt; Process 'command 'D:\All Data\Softwares\Latest Flutter\flutter\bin\flutter.bat'' finished with non-zero exit value 1
  
  * Try:
  Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.
  
  * Get more help at https://help.gradle.org
  
  BUILD FAILED in 3m 57s
  Running Gradle task 'assembleRelease'...                          240.3s
  Exception: Gradle task assembleRelease failed with exit code 1
  </code></pre>
  <p>This file is also automatically generated with errors:</p>
  <pre><code>//
  // Generated file. Do not edit.
  //
  
  // ignore_for_file: directives_ordering
  // ignore_for_file: lines_longer_than_80_chars
  
  import 'package:blue_thermal_printer/';
  import 'package:cloud_firestore_web/cloud_firestore_web.dart';
  import 'package:cloud_functions_web/cloud_functions_web.dart';
  import 'package:connectivity_for_web/connectivity_for_web.dart';
  import 'package:firebase_analytics_web/firebase_analytics_web.dart';
  import 'package:firebase_auth_web/firebase_auth_web.dart';
  import 'package:firebase_core_web/firebase_core_web.dart';
  import 'package:firebase_messaging_web/firebase_messaging_web.dart';
  import 'package:firebase_storage_web/firebase_storage_web.dart';
  import 'package:fluttertoast/fluttertoast_web.dart';
  import 'package:geolocator_web/geolocator_web.dart';
  import 'package:google_maps_flutter_web/google_maps_flutter_web.dart';
  import 'package:google_sign_in_web/google_sign_in_web.dart';
  import 'package:image_picker_for_web/image_picker_for_web.dart';
  import 'package:maps_launcher/maps_launcher_web.dart';
  import 'package:shared_preferences_web/shared_preferences_web.dart';
  import 'package:url_launcher_web/url_launcher_web.dart';
  import 'package:video_player_web/video_player_web.dart';
  
  import 'package:flutter_web_plugins/flutter_web_plugins.dart';
  
  // ignore: public_member_api_docs
  void registerPlugins(Registrar registrar) {
    BlueThermalPrinterPlugin.registerWith(registrar);
    FirebaseFirestoreWeb.registerWith(registrar);
    FirebaseFunctionsWeb.registerWith(registrar);
    ConnectivityPlugin.registerWith(registrar);
    FirebaseAnalyticsWeb.registerWith(registrar);
    FirebaseAuthWeb.registerWith(registrar);
    FirebaseCoreWeb.registerWith(registrar);
    FirebaseMessagingWeb.registerWith(registrar);
    FirebaseStorageWeb.registerWith(registrar);
    FluttertoastWebPlugin.registerWith(registrar);
    GeolocatorPlugin.registerWith(registrar);
    GoogleMapsPlugin.registerWith(registrar);
    GoogleSignInPlugin.registerWith(registrar);
    ImagePickerPlugin.registerWith(registrar);
    MapsLauncherWeb.registerWith(registrar);
    SharedPreferencesPlugin.registerWith(registrar);
    UrlLauncherPlugin.registerWith(registrar);
    VideoPlayerPlugin.registerWith(registrar);
    registrar.registerMessageHandler();
  }
  </code></pre>
  <p>As well I constantly see these errors in dart analysis :</p>
  <pre><code>error: Target of URI doesn't exist: 'package:blue_thermal_printer/'. (uri_does_not_exist at [food_delivery_app] lib\generated_plugin_registrant.dart:8)
  error: Undefined name 'BlueThermalPrinterPlugin'. (undefined_identifier at [food_delivery_app] lib\generated_plugin_registrant.dart:31)
  </code></pre>
  <p>However in debug mode, the app works fine.
  And when I remove bluetooth_thermal_print package, it works fine as well too.
  What could be the issue? How can I release my app with this package?</p>