bug#53321: 28.0.91; Add a defcustom option to ruby-do-end-to-brace function for ruby-mode

[Billy.Zheng]

Hi, I want to report,  add a defcustom option to ruby-do-end-to-brace function 
ruby for
emacs builtin mode, as said in source code line 1725.


```
      (goto-char orig)
      (delete-char 2)
      ;; Maybe this should be customizable, let's see if anyone asks.
      (insert "{ ")
      (setq beg-marker (point-marker))
```

And, please check some discuss on this github link.

https://github.com/dgutov/robe/issues/136#issuecomment-1013910661

-- 
Thanks,
Billy