Add missing changelog note for telepath streamfield

CHANGELOG.txt

@@ -4,6 +4,7 @@ Changelog
 2.13 (xx.xx.xxxx) - IN DEVELOPMENT
 ~~~~~~~~~~~~~~~~~
 
+ * New StreamField implementation with performance and functionality improvements (Matt Westcott, Karl Hobley)
  * Added a simple translation module into `wagtail.contrib.simple_translation` (Coen van der Kamp)
  * Support passing `min_num`, `max_num` and `block_counts` arguments directly to `StreamField` (Haydn Greatnews, Matt Westcott)
  * Add the option to set rich text images as decorative, without alt text (Helen Chapman, Thibaud Colas)