Added DALL.E 3 to readme.md (#741)

* Added DALL.E 3 to readme.md

Added DALL.E 3 to readme.md as its supported now as per issue https://github.com/sashabaranov/go-openai/issues/494

* Update README.md

---------

Co-authored-by: Alexander Baranov <677093+sashabaranov@users.noreply.github.com>

README.md

@@ -7,7 +7,7 @@ This library provides unofficial Go clients for [OpenAI API](https://platform.op
 
 * ChatGPT
 * GPT-3, GPT-4
-* DALL·E 2
+* DALL·E 2, DALL·E 3
 * Whisper
 
 ## Installation