Fix marks being cleared on selection events (#2158)

packages/slate-react/src/plugins/after.js

@@ -677,6 +677,10 @@ function AfterPlugin() {
       if (next) range = range.moveFocusTo(next.key, 0)
     }
 
+    // Preserve active marks from the current selection.
+    // They will be cleared by `change.select` if the selection actually moved.
+    range = range.set('marks', value.selection.marks)
+
     let selection = document.createSelection(range)
     selection = selection.setIsFocused(true)
     change.select(selection)