style fix: add css var `--color-level-6` for light theme (#7337)

resources/css/common.css

@@ -183,6 +183,7 @@ html[data-theme='light'] {
   --color-level-3: var(--ls-quaternary-background-color);
   --color-level-4: #d0e6fa;
   --color-level-5: #bbdaf6;
+  --color-level-6: #a7cef1;
 }
 
 html:not(.is-native-android) {

src/main/frontend/components/block.css

@@ -465,7 +465,7 @@
 }
 
 .color-level .color-level .color-level .color-level .color-level .color-level {
-  background-color: var(--color-level-3);
+  background-color: var(--color-level-6);
 }
 
 .color-level .color-level .color-level .color-level .color-level .color-level .color-level {
@@ -477,7 +477,7 @@
 }
 
 .color-level .color-level .color-level .color-level .color-level .color-level .color-level .color-level .color-level {
-  background-color: var(--color-level-3);
+  background-color: var(--color-level-6);
 }
 
 .color-level .color-level .color-level .color-level .color-level .color-level .color-level .color-level .color-level .color-level {