added ff release note for light-dark images (#43708)

* added ff release note for light-dark images

* Update files/en-us/mozilla/firefox/releases/150/index.md

Co-authored-by: Dipika Bhattacharya <dipika@foss-community.org>

---------

Co-authored-by: Dipika Bhattacharya <dipika@foss-community.org>

Author: dletorey

files/en-us/mozilla/firefox/releases/150/index.md

@@ -32,7 +32,10 @@ Firefox 150 is the current [Beta version of Firefox](https://www.firefox.com/en-
 
 <!-- #### Removals -->
 
-<!-- ### CSS -->
+### CSS
+
+- The [`light-dark()`](/en-US/docs/Web/CSS/Reference/Values/color_value/light-dark) CSS function now accepts [`<image>`](/en-US/docs/Web/CSS/Reference/Values/image) values. This allows using images, gradients, and so on for different color schemes.
+  ([Firefox bug 2023569](https://bugzil.la/2023569)).
 
 <!-- #### Removals -->