Add a multiline input option for the chat prompt

[nickrttn]

Is your feature request related to a problem? Please describe.

Long prompts are hard to read back when revisiting a conversation because they cannot be formatted in any way.

Describe the solution you'd like

Adding an option to enable a multiline (Markdown) text input on the Markprompt component.

Allows for formatting in prompts by adding line breaks (and possibly more using Markdown).