[rb] add IE driver extensions

Author: titusfortner

rb/lib/selenium/webdriver/common/driver.rb

@@ -346,6 +346,8 @@ def add_extensions(browser)
                        Firefox::Driver::EXTENSIONS
                      when :safari, :safari_technology_preview
                        Safari::Driver::EXTENSIONS
+                     when :ie, :internet_explorer
+                       IE::Driver::EXTENSIONS
                      else
                        []
                      end