docs: add assistant guidelines

[Martin-Hoppe]

Fixes #134

[mirkolenz]

The content looks good, thank you! I did some formatting and renamed the file. One thing to be added to this guide could be a small explanation of the new parameters the assistant now has. These mostly mimic the OpenAI API Parameters as described here: https://platform.openai.com/docs/api-reference/chat/create

Would be nice to have concise descriptions for these so that non-developers get an idea how to tweak the output.

[mirkolenz]

Thanks, the new descriptions are looking good! One last thing that came to my mind: Could you add some more information the the two example workflows based on your experience (i.e., which types of texts work good for generating the entire graph, which ones would require the user to perform the steps individually and correct potential errors). Thank you!