Add Intro to Social Networks Textbook by Lizardo and Jilbert 2023

[bduckles]

Suggestion to add the open introductory textbook on social networks "Social Networks an Introduction" by Lizardo and Jilbert (2023) to the list.

• Website: https://olizardo.github.io/networks-textbook/
• Source: https://github.com/olizardo/networks-textbook/tree/main