✨ Feature(textarea): (Somehow) add the option to send or format user message as plain text instead of getting auto-formatted as markdown

[KemingHe]

Current implementation can be very annoying when what user entered gets shown differently (compared to what's typed in chat) through the markdown renderer.

The solution should NOT necessarily be a code block, it could be a styled-markdown variant or a custom text 1-to-1 renderer.

[KemingHe]

To further minimize footprint, could set this as default for all user messages. Again, only a rendering mechanism, doesn't (and shouldn't) affect functionality.