Adding sponsorship info and a book link.

Author: trekhleb

README.md

@@ -303,3 +303,20 @@ Below is the list of some of the most used Big O notations and their performance
 | **Shell sort**        | n&nbsp;log(n)   | depends on gap sequence   | n&nbsp;(log(n))<sup>2</sup>  | 1         | No         |           |
 | **Counting sort**     | n + r           | n + r               | n + r               | n + r     | Yes       | r - biggest number in array |
 | **Radix sort**        | n * k           | n * k               | n * k               | n + k     | Yes       | k - length of longest key |
+
+## Supporting the project
+
+You may support this project via ❤️️ [GitHub](https://github.com/sponsors/trekhleb) or ❤️️ [Patreon](https://www.patreon.com/trekhleb).
+
+## JavaScript Algorithms Book
+
+<table>
+    <tr>
+        <td>
+            [![JavaScript Algorithms Book](https://raw.githubusercontent.com/trekhleb/javascript-algorithms/master/assets/js-algorithms-book-cover-xs.png)](https://www.newline.co/javascript-algorithms)
+        </td>
+        <td>
+            Recently we've released a [JavaScript Algorithms Book](https://www.newline.co/javascript-algorithms) which contains detailed explanations of many popular algorithms and data structures implemented on JavaScript. You can check the full list of topics that are covered in the book and download the first chapter [here](https://www.newline.co/javascript-algorithms).
+        </td>
+    </tr>
+</table>