text: Title: New keyboard shortcuts and config file options
  Body: ### Description
  
  I am hoping to be able to:
  
  1. Give some keyboard commands to fold/unfold all markdown headers in a notebook.
  2. Create a setting in the config file, to make all headers folded by default, on opening a notebook.
  3. Make a setting in the config file, so that all newly created cells are viewed as markdown by default.
  
  ### Suggested solution
  
  Make more keyboard shortcuts and extra config file options.
  
  Thanks for the great notebooks!
  
  ### Alternative
  
  _No response_
  
  ### Additional context
  
  _No response_