2 feature requests: "intertext" and REPL output support

[tikuma-lsuhsc]

Just found this extension, and I really like the :context: option.

Trying this extension for a bit, I have a couple features that would enhance its output IMHO.

1. :intertext: option (similar to \intertext LaTeX math command) to insert a (paragraph) text between 2 blocks.

   For example

   .. exec::
   :intertext: outputs
   
   x = 5
   print(f'{x=}')

   to expand to rst code:

   ::
   x = 5
   print(f'{x=}')
   
   outputs
   
   ::
   x=5

2. :repl: option Run the code as if running it in the interpreter

   This option enables formatting the code lines as a doctest_block. If a line is free of any assignment operator, print the output of __repl__() of the line output.

   Using the same example from above,

   .. exec::
   :repl: true
   
   x = 5
   f'{x=}' # no print()

produces

  >>> x = 5
  >>> f'{x=}' # no print()

  ::

    'x=5'

What do you think?

[yongrenjie]

Hello! Thanks for this :) this extension is hardly a complete work, so there's tons of room for improvement. I like both of your suggestions! I'm not sure I have the time to implement it right now but if you feel like doing a PR, I'd be more than happy to look, and if not I could look to get around to it some time soon.

[tikuma-lsuhsc]

Glad you like these ideas! I don't know much about sphinx extensions atm but I'll look into it and see if I can cook something up.