fix: prevent nested bullet list icon rendering as emoji on iOS 18+ (#2394) (#2399)

Add Unicode Variation Selector 15 (U+FE0E) to the Black Small Square
character (U+25AA) used for level 3+ nested bullet lists. This forces
text presentation instead of emoji presentation on iOS 18+, which
otherwise renders it as a large black square emoji.

Author: bxff

packages/core/src/editor/Block.css

@@ -372,7 +372,7 @@ NESTED BLOCKS
   > .bn-block-outer[data-prev-type="bulletListItem"]
   > .bn-block
   > .bn-block-content::before {
-  content: "▪";
+  content: "▪\FE0E";
 }
 
 [data-content-type="bulletListItem"]
@@ -390,7 +390,7 @@ NESTED BLOCKS
   > .bn-block
   > div[data-type="modification"]
   > .bn-block-content[data-content-type="bulletListItem"]::before {
-  content: "▪";
+  content: "▪\FE0E";
 }
 
 /* CODE BLOCKS */