feat(r): Plotting capability

[oacar]

This might be out of scope for this project, so feel free to close this if so.

I am aware of some commercial solutions that provides plotting within their data chat experiences (datachat, snowflake intelligence etc.), so I thought this could be a nice feature to add.

I added a

• ui component to render ggplot within the chat,
• a function to evaluate ggplot2 code generated by LLM
• registered a new tool called update_plot.
• utilized callr to run the plotting as a way to increase security of running arbitrary code and added guardrails to the prompt.