Implement correct WP plugin meta

See https://codex.wordpress.org/File_Header#Plugin_File_Header_Example

Author: szepeviktor

class-wp-bootstrap-navwalker.php

@@ -1,12 +1,10 @@
 <?php
 /**
- * WP Bootstrap Navwalker
+ * WP Bootstrap Navwalker.
  *
  * @package WP-Bootstrap-Navwalker
- */
-
-/*
- * Class Name: WP_Bootstrap_Navwalker
+ *
+ * @wordpress-plugin
  * Plugin Name: WP Bootstrap Navwalker
  * Plugin URI:  https://github.com/wp-bootstrap/wp-bootstrap-navwalker
  * Description: A custom WordPress nav walker class to implement the Bootstrap 4 navigation style in a custom theme using the WordPress built in menu manager.
@@ -20,7 +18,7 @@
 */
 
 /* Check if Class Exists. */
-if ( ! class_exists( 'WP_Bootstrap_Navwalker' ) ) {
+if ( ! class_exists( 'WP_Bootstrap_Navwalker' ) ) :
 	/**
 	 * WP_Bootstrap_Navwalker class.
 	 *
@@ -552,4 +550,4 @@ private function linkmod_element_close( $linkmod_type ) {
 			return $output;
 		}
 	}
-}
+endif;