Add missing changelog entry

Author: Jannik Zschiesche

CHANGELOG.md

@@ -34,6 +34,7 @@
 *   (improvement) Allow `++` in JS/TS code.
 *   (improvement) The code is now always compiled per entry file
 *   (improvement) Ignore `.css` files when compiling webpack. You need to import them manually in your SCSS.
+*   (improvement) Build TypeScript for the `esnext` module system, that (amongst other things) allows to use `import()`.
 
 
 8.1.0