text: Title: Support disabling mo.ui.chat input
  Body: ### Description
  
  I was hoping to make my chatbot disabled until the user entered an api key in another input but didn't see any parameter to disable the input.
  
  ### Suggested solution
  
  Support disabled parameter on the Chat input.
  
  When set to true it can create a non interactive overlay over the input.
  
  Html now supports inert attribute to disable interactions inside an element. Inert elements can be styled to achieve the disabled styling.
  
  See: https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/inert
  
  ### Alternative
  
  Currently using mo.stop to not show the cell at all. 
  
  ### Additional context
  
  Here's the notebook where I want to use this: 
  
  https://aszenz.github.io/kashmiri-chatbot/
  
  By not showing the input, I have a feeling people won't understand how the chatbot looks like.