Update CHANGELOG.md

Author: brizental

CHANGELOG.md

@@ -5,6 +5,7 @@
 * [#856](https://github.com/mozilla/glean.js/pull/860): Implement the `PlatformInfo` module for the web platform.
   * Out of `os`, `os_version`, `architecture` and `locale`, on the web platform, we can only retrive `os` and `locale` information. The other information will default to the known value `Unknown` for all pings coming from this platform.
 * [#856](https://github.com/mozilla/glean.js/pull/856): Expose the `@mozilla/glean/web` entry point for using Glean.js in websites.
+* [#908](https://github.com/mozilla/glean.js/pull/908): Provide actionable error message in case uploadEnabled is undefined.
 
 # v0.23.0 (2021-10-12)