Update CHANGELOG.md to reflect UIScrollArea enhancements and UIDropdown positioning fix

Author: eruvanos

CHANGELOG.md

@@ -9,7 +9,9 @@ Arcade [PyPi Release History](https://pypi.org/project/arcade/#history) page.
 - Adds a new `arcade.NoAracdeWindowError` exception type. This is raised when certain window operations are performed and there is no valid Arcade window found. Previously where this error would be raised, we raised a standard `RuntimeError`, this made it harder to properly catch and act accordingly. This new exception subclasses `RuntimeError`, so you can still catch this error the same way as before. The `arcade.get_window()` function will now raise this if there is no window.
 - Along with the new exception type, is a new `arcade.windows_exists()` function which will return True or False based on if there is currently an active window.
 - GUI
-  - `UIManager` did not apply size hint of (0,0). Mainly an issue with `UIBoxLayout`.  
+  - `UIManager` did not apply size hint of (0,0). Mainly an issue with `UIBoxLayout`.
+  - Allow multiple children in `UIScrollArea`.
+  - Fix `UIDropdown Overlay` positioning within a `UIScrollArea`.
 
 ## 3.3.3