Update README

Author: 小野 直人

README.md

@@ -487,6 +487,7 @@ config set no_color true
   * `RUBY_DEBUG_SOCK_DIR` (`sock_dir`): UNIX Domain Socket remote debugging: socket directory
   * `RUBY_DEBUG_COOKIE` (`cookie`): Cookie for negotiation
   * `RUBY_DEBUG_OPEN_FRONTEND` (`open_frontend`): frontend used by open command (vscode, chrome, default: rdbg).
+  * `RUBY_DEBUG_CHROME_PATH` (`chrome_path`): Google Chrome path
 
 * OBSOLETE
   * `RUBY_DEBUG_PARENT_ON_FORK` (`parent_on_fork`): Keep debugging parent process on fork (default: false)