Syntax highlighting of code diff paragraphs in message bodies

[rjd15372]

To improve the visibility of inline code diffs present in message bodies, we could add diff syntax highlighting to the diff.

[ImTheKai]

How do you envision this to look like? Just the simple green line for a + and red for a -, or something fancier? Just trying to clarify the need.

[rjd15372]

Yeah, green/red colors is enough.

[ImTheKai]

Got implemented by #64