Add JS book subscription link.

trekhleb · trekhleb · commit a3dce1674c69 · 2018-07-20T22:42:04.000+03:00
diff --git a/README.md b/README.md
@@ -14,6 +14,8 @@ _Read this in other languages:_
 [简体中文](README.zh-CN.md),
 [繁體中文](README.zh-TW.md)
 
+> [Be notified when the JavaScript Algorithms book launches](https://upscri.be/402324/)
+
 ## Data Structures
 
 A data structure is a particular way of organizing and storing data in a computer so that it can
