added color content background featured colors

src/themes/_color.dark.css

@@ -2,6 +2,7 @@
   /* Content background */
   --color-content-background-primary: #292d30;
   --color-content-background-secondary: #25282a;
+  --color-content-background-featured: #292929;
 
   /* State */
   --color-state-hover: #31373e;

src/themes/_color.light.css

@@ -2,6 +2,7 @@
   /* Content background */
   --color-content-background-primary: #ffffff;
   --color-content-background-secondary: #f7f7f7;
+  --color-content-background-featured: #EDEBE9;
 
   /* State */
   --color-state-hover: #f3f2f1;

src/themes/readme.md

@@ -11,6 +11,7 @@ The files have the following structure:
   /* Content background */
   --color-content-background-primary // Content area, command bar background, tiles background, cards background
   --color-content-background-secondary // background for panel and dashboard, color for placeholder on tiles in edit mode
+  --color-content-background-featured // Background color for the area behind featured items to make them stand out more
 
   /* State */
   --color-state-hover // hover, focus