Support Dart syntax higlighting

[JaredEzz]

Validations

• [X] I believe this is a way to improve. I'll try to join the Continue Discord for questions
• [X] I'm not able to find an open issue that requests the same enhancement

Problem

Other languages have syntax highlighting in the Continue response that make reading and using the response much more helpful.

Dart (and I'm sure other languages) do not have this support

The expected code highlighting would look something like this

Solution

Add support for Dart and other languages for syntax highlighting in the response