fix environment needs

README.md

@@ -1,4 +1,4 @@
-# ipycytoscape
+f# ipycytoscape
 
 [![Tests](https://github.com/cytoscape/ipycytoscape/actions/workflows/test.yml/badge.svg)](https://github.com/cytoscape/ipycytoscape/actions/workflows/test.yml) [![Documentation Status](https://readthedocs.org/projects/ipycytoscape/badge/?version=master)](https://ipycytoscape.readthedocs.io/en/latest/?badge=master) [![StackOverflow](https://img.shields.io/badge/stackoverflow--orange.svg)](https://stackoverflow.com/questions/tagged/ipycytoscape) [![Join the chat at https://gitter.im/QuantStack/Lobby](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/QuantStack/Lobby?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 
@@ -155,7 +155,7 @@ pip install -e ".[test]"
 Or with conda/mamba:
 
 ```
-mamba -c conda-forge install networkx pandas nbval pytest
+mamba -c conda-forge install networkx pandas nbval pytest ipywidgets=7
 ```
 
 #### And to run it: