Add example of displaying custom usage in subcommand list

examples/help-subcommands-usage.js

@@ -0,0 +1,29 @@
+// const commander = require('commander'); // (normal include)
+const commander = require('../'); // include commander in git clone of commander repo
+
+// By default the subcommand list includes a fairly simple usage. If you have added a custom usage
+// to the subcommands you may wish to configure the help to show these instead.
+//
+// See also ./configure-help.js which shows configuring the subcommand list to have no usage at all
+// and just the subcommand name.
+
+const program = new commander.Command()
+  .configureHelp({ subcommandTerm: (cmd) => cmd.name() + ' ' + cmd.usage() });
+
+program.command('make <FILENAME>')
+  .usage('-root ROOTDIR [-abc] <FILENAME>')
+  .requiredOption('--root <ROOTDIR>')
+  .option('-a')
+  .option('-b')
+  .option('-c')
+  .summary('example command with custom usage')
+  .description('this full description is  displayed in the full help and not in the list of subcommands');
+
+program.command('serve <SERVICE>')
+  .option('--port <PORTNUMBER>')
+  .description('example command with default simple usage');
+
+program.parse();
+
+// Try the following:
+//    node help-subcommands-usage help