Fix tutorial and jupyter docs

[amn41]

Proposed changes:

• bump to rasabaster 0.7.21
• some improvements to jupyter notebooks docs
• fixes user guide > rasa tutorial > unable to run examples #3934
• fixes Broken links in your documentation #3952
• fixes Example code on api/jupyter-notebooks fails to run properly #3579

Status (please check what you already did):

• made PR ready for code review
• added some tests for the functionality
• updated the documentation
• updated the changelog
• reformat files using black (please check Readme for instructions)

[erohmensing]

Looks like it is failing because of these warnings:

/Users/erohmensing/rasa/docs/api/jupyter-notebooks.rst:30: WARNING: Error in "runnable" directive:
unknown option: "language".

.. runnable::
   :language: python

   config = "config.yml"
   training_files = "data/"
   domain = "domain.yml"
   output = "models/"
   print(config, training_files, domain, output)

as well as this one:

/Users/erohmensing/rasa/docs/api/jupyter-notebooks.rst:69: WARNING: Error in "runnable" directive:
invalid option block.

.. runnable::
   :language: python
   from rasa.jupyter import chat
   chat(model_path)

[erohmensing]

Sorry, i tried to fix it myself without understanding that you're working on fixing it in the rasabaster repo i believe 😅feel free to revert my changes

[erohmensing]

Looks good! The only thing I would think about adding is a note saying that if they want to run the code in their own notebook, not to copy the python in the code (since jupyter is a good platform for beginners)

[erohmensing]

Nevermind, this shouldn't be merged yet, the code still isn't working. Will fix

[erohmensing]

@amn41 I’ve figured out how to fix the kernel code for jupyter notebooks (rasabaster PR review request incoming), but there are still other fixes (even to rasa) that need to go in to make it work. I propose that we send out this PR to fix the tutorial for 0.7.21 and temporarily hide the jupyter docs till they work again on rasabaster 0.7.22 and updated docs-binder requirements.

I’m tracking the jupyter stuff here: https://github.com/RasaHQ/customers/issues/128

Sound good?