Update changelog

Author: Cleptomania

CHANGELOG.md

@@ -5,6 +5,10 @@ Arcade [PyPi Release History](https://pypi.org/project/arcade/#history) page.
 
 ## Unreleased
 
+- PyInstaller
+  - Fixed an issue where imports for backends for the `arcade.gl` package could not be discovered by PyInstaller.
+    Since 3.3.0 users have needed to add these hidden imports via the pyinstaller CLI in order for Arcade to work.
+
 - GUI
   - Fix a bug, where the caret of UIInputText was misplaced after resizing the widget
   - Use incremental layout for UIScrollArea to improve performance of changing text