improvement(app), display the app list when running "bit app" without a subcommand

scopes/harmony/application/app.cmd.ts

@@ -30,17 +30,18 @@ export class AppListCmd implements Command {
 }
 
 export class AppCmd implements Command {
-  name = 'app <sub-command>';
+  name = 'app [sub-command]';
   description = 'Manages apps';
   helpUrl = 'docs/getting-started/composing/create-apps';
   alias = 'apps';
   group = 'apps';
   commands: Command[] = [];
   options = [] as CommandOptions;
 
+  constructor(private applicationAspect: ApplicationMain) {}
+
   // eslint-disable-next-line @typescript-eslint/no-unused-vars
   async report(args: [string]) {
-    // it should never be here. Yargs throws an error before reaching this method.
-    return `Please specify a sub-command`;
+    return new AppListCmd(this.applicationAspect).report();
   }
 }

scopes/harmony/application/application.main.runtime.ts

@@ -517,7 +517,7 @@ export class ApplicationMain {
       harmony
     );
     appService.registerAppType = application.registerAppType.bind(application);
-    const appCmd = new AppCmd();
+    const appCmd = new AppCmd(application);
     appCmd.commands = [new AppListCmd(application), new RunCmd(application, logger)];
     aspectLoader.registerPlugins([new AppPlugin(appSlot)]);
     builder.registerBuildTasks([new AppsBuildTask(application)]);