Mention compatible Diofant version

[LunDev]

The only place I have found describing the required dependencies is in the readme:

5. Install the required dependencies with pip:

pip install scipy
pip install diofant
pip install lark-parser

Unfortunately, the default and currrently latest Diofant version (0.12.0) doesn't appear to be compatible and an explicit installation of 0.11.0 (pip install diofant==0.11.0) seems required. It would be great to save uses this trial-and-error and list this in the readme or even create something like a requirements.txt as the other two dependencies might also introduce breaking changes at some point.

Python version: 3.9.2