Add feature for opening/activating default browser

[mshafer-NI]

Would be nice if we could just have the default browser easily at hand: https://www.autohotkey.com/board/topic/67330-how-to-open-default-web-browser/

Could use something like this:

   default_browser := DefaultBrowser()
   parts := StrSplit(default_browser, "\")
   name := parts.Pop()
   msgBox, name is %name%
   return