Add --license arg to package-readme command

Follow-up to #276 and 72fd665

Author: swissspidy

README.md

@@ -194,7 +194,7 @@ WP-CLI Behat framework uses Behat ~2.5, which is installed with Composer.
 Generate a README.md for your command.
 
 ~~~
-wp scaffold package-readme <dir> [--force] [--branch=<branch>]
+wp scaffold package-readme <dir> [--force] [--branch=<branch>] [--license=<license>]
 ~~~
 
 Creates a README.md with Using, Installing, and Contributing instructions
@@ -279,6 +279,12 @@ In this example:
 	[--branch=<branch>]
 		Name of default branch of the underlying repository. Defaults to main.
 
+	[--license=<license>]
+		License for the package.
+		---
+		default: MIT
+		---
+
 
 
 ### wp scaffold package-github

src/ScaffoldPackageCommand.php

@@ -250,6 +250,12 @@ public function package( $args, $assoc_args ) {
 	 * [--branch=<branch>]
 	 * : Name of default branch of the underlying repository. Defaults to main.
 	 *
+	 * [--license=<license>]
+	 * : License for the package.
+	 * ---
+	 * default: MIT
+	 * ---
+	 *
 	 * @when before_wp_load
 	 * @subcommand package-readme
 	 */
@@ -285,6 +291,7 @@ public function package_readme( $args, $assoc_args ) {
 			'has_commands'                  => false,
 			'wp_cli_update_to_instructions' => 'the latest stable release with `wp cli update`',
 			'show_powered_by'               => isset( $composer_obj['extra']['readme']['show_powered_by'] ) ? (bool) $composer_obj['extra']['readme']['show_powered_by'] : true,
+			'license'                       => $assoc_args['license'],
 		];
 
 		if ( isset( $composer_obj['extra']['readme']['shields'] ) ) {