Add changelog entry

Author: jorgefilipecosta

packages/base-styles/CHANGELOG.md

@@ -10,6 +10,10 @@
 
 -   `outset-ring__focus`: Allow overriding the focus ring color via the `--focus-color` custom property ([#80587](https://github.com/WordPress/gutenberg/pull/80587)).
 
+### Bug Fixes
+
+-   Lower the editor z-index of left/right aligned blocks below sticky and fixed position blocks, so floated blocks no longer cover stuck blocks while scrolling ([#80749](https://github.com/WordPress/gutenberg/pull/80749)).
+
 ### Internal
 
 -   Update `exports` to use subpath patterns instead of deprecated trailing `/` folder mappings ([#80270](https://github.com/WordPress/gutenberg/pull/80270)).