Add support for matching delimiter blinking

[ralexstokes]

I would like rustyline to blink the matching delimiter once I type it. Is there any reason you see why this shouldn't work in the library? Otherwise, I can put together a pull request.

I would think to start with () but I don't see an immediate reason to not add {} []. Perhaps it should be configurable for the user?

[gwenn]

Should be possible with Highlighter trait introduced in 2.0.
I will give it a try.

[gwenn]

3.0.0 released.