feat: improve create command usage (#84)

README.md

@@ -70,7 +70,8 @@ Global options:
           [true]     Enable anonymous usage statistics
 
 Available commands:
-  create   Creates a new very good flutter application in seconds.
+  create   very_good create <output directory>
+           Creates a new very good flutter project in the specified directory.
 
 Run "very_good help <command>" for more information about a command.
 ```

lib/src/commands/create.dart

@@ -46,11 +46,17 @@ class CreateCommand extends Command<int> {
   final Future<MasonGenerator> Function(MasonBundle) _generator;
 
   @override
-  final String description =
-      'Creates a new very good flutter application in seconds.';
+  String get description =>
+      'Creates a new very good flutter project in the specified directory.';
 
   @override
-  final String name = 'create';
+  String get summary => '$invocation\n$description';
+
+  @override
+  String get name => 'create';
+
+  @override
+  String get invocation => 'very_good create <output directory>';
 
   /// [ArgResults] which can be overridden for testing.
   @visibleForTesting

test/src/command_runner_test.dart

@@ -28,7 +28,8 @@ const expectedUsage = [
       '          [true]     Enable anonymous usage statistics\n'
       '\n'
       'Available commands:\n'
-      '  create   Creates a new very good flutter application in seconds.\n'
+      '  create   very_good create <output directory>\n'
+      '''           Creates a new very good flutter project in the specified directory.\n'''
       '\n'
       'Run "very_good help <command>" for more information about a command.'
 ];