Add .DS_Store to .gitignore in directory generator

Author: mdmintz

seleniumbase/console_scripts/sb_mkdir.py

@@ -274,6 +274,7 @@ def main():
     data.append("saved_cookies")
     data.append("recordings")
     data.append("visual_baseline")
+    data.append(".DS_Store")
     data.append("selenium-server-standalone.jar")
     data.append("proxy.zip")
     data.append("proxy.lock")