Add Message Preview

### Your use case

How about adding a preview feature to live show the rendering result of formatting and LaTeX equations?

A cool workaround is to make it so that the effect of Markdown formatting (bold, italic, etc.) is displayed together with the syntax during editing. This means something like

xxx **\*\*abc\*\*** xxx *\*def\** xxx

And for LaTeX equations, when the cursor is located at an equation, its source code is revealed, otherwise the rendered equation is shown.

With all this the user would not have to gamble on the final result and then edit the message again when something was wrong.

### Have you considered any alternatives?

_No response_

### Additional context

_No response_