text: Title: Show alias function description using superhelp
  Body: Enrich [superhelp](https://xon.sh/tutorial.html#help-superhelp-with) by showing the alias function description.
  
  ```xsh
  @aliases.register("hello")
  def _alias_hello():
      """Show world."""
      print('world')
  
  hello
  # world
  
  # Now:
  hello?
  # Unknown locale, assuming C
  # No manual entry for hello
  
  # Proposed:
  hello?
  # Alias description:
  # Show world.
  ```
  
  This is simple to implement by getting the docstring from aliases and name:
  ```python
  aliases['hello'].__doc__
  # Show world.
  ```
  
  ## For community
  ⬇️  **Please click the 👍 reaction instead of leaving a `+1` or 👍  comment**
  