JS: Add change note

Author: asger-semmle

change-notes/1.21/analysis-javascript.md

@@ -13,6 +13,8 @@
 
 * The security queries now track data flow through Base64 decoders such as the Node.js `Buffer` class, the DOM function `atob`, and a number of npm packages intcluding [`abab`](https://www.npmjs.com/package/abab), [`atob`](https://www.npmjs.com/package/atob), [`btoa`](https://www.npmjs.com/package/btoa), [`base-64`](https://www.npmjs.com/package/base-64), [`js-base64`](https://www.npmjs.com/package/js-base64), [`Base64.js`](https://www.npmjs.com/package/Base64) and [`base64-js`](https://www.npmjs.com/package/base64-js).
 
+* The security queries now track data flow through exceptions.
+
 * The security queries now treat comparisons with symbolic constants as sanitizers, resulting in fewer false positives.
 
 * TypeScript 3.4 features are now supported.