feat: add a longer no-op message. (#218)

This is a common source of confusion, hopefully this will help.

shorebird_code_push/lib/src/shorebird_code_push_noop.dart

@@ -11,6 +11,9 @@ class ShorebirdCodePushNoop implements ShorebirdCodePushBase {
     // ignore: avoid_print
     print('''
 [ShorebirdCodePush]: Shorebird Engine not available, using no-op implementation.
+This occurs when using package:shorebird_code_push in an app that does not
+contain the Shorebird Engine. Most commonly this is due to building with
+`flutter build` or `flutter run` instead of `shorebird release`.
 ''');
   }
   @override

shorebird_code_push/test/shorebird_code_push_io_test.dart

@@ -37,7 +37,11 @@ void main() {
         printLogs,
         equals(
           [
-            '''[ShorebirdCodePush]: Shorebird Engine not available, using no-op implementation.\n''',
+            '''
+[ShorebirdCodePush]: Shorebird Engine not available, using no-op implementation.
+This occurs when using package:shorebird_code_push in an app that does not
+contain the Shorebird Engine. Most commonly this is due to building with
+`flutter build` or `flutter run` instead of `shorebird release`.\n''',
           ],
         ),
       );
@@ -57,7 +61,11 @@ void main() {
         printLogs,
         equals(
           [
-            '''[ShorebirdCodePush]: Shorebird Engine not available, using no-op implementation.\n''',
+            '''
+[ShorebirdCodePush]: Shorebird Engine not available, using no-op implementation.
+This occurs when using package:shorebird_code_push in an app that does not
+contain the Shorebird Engine. Most commonly this is due to building with
+`flutter build` or `flutter run` instead of `shorebird release`.\n''',
           ],
         ),
       );

shorebird_code_push/test/src/shorebird_code_push_noop_test.dart

@@ -23,7 +23,9 @@ void main() {
     test('logs warning when instantiated', () {
       const expected = '''
 [ShorebirdCodePush]: Shorebird Engine not available, using no-op implementation.
-''';
+This occurs when using package:shorebird_code_push in an app that does not
+contain the Shorebird Engine. Most commonly this is due to building with
+`flutter build` or `flutter run` instead of `shorebird release`.\n''';
       expect(printLogs, equals([expected]));
     });