Add Data Structures and Information Retrieval in Python by Allen B. Downey to README (#9737)

books/free-programming-books-langs.md

@@ -1951,6 +1951,7 @@ Books on general-purpose programming that don't focus on a specific language are
 * [Computational and Inferential Thinking](https://inferentialthinking.com/chapters/intro.html) - Ani Adhikari, John DeNero, David Wagner (HTML)
 * [Cracking Codes with Python](https://inventwithpython.com/cracking/) - Al Sweigart (3.6)
 * [Data Structures and Algorithms in Python](https://web.archive.org/web/20161016153130/http://www.brpreiss.com/books/opus7/html/book.html) - B. R. Preiss (PDF) *(:card_file_box: archived)*
+* [Data Structures and Information Retrieval in Python](https://greenteapress.com/wp/data-structures-and-information-retrieval-in-python/) - Allen B. Downey
 * [Dive into Python 3](https://diveintopython3.problemsolving.io) - Mark Pilgrim (3.0)
     * [Dive into Python](https://linux.die.net/diveintopython/html/toc/index.html) - Mark Pilgrim (2.3)
 * [Essential Python](https://www.programming-books.io/essential/python/) - Krzysztof Kowalczyk, StackOverflow Contributors