Overwork documentation (#4516)

docs/mkdocs/docs/api/basic_json/emplace.md

@@ -14,6 +14,11 @@ created from `args`.
 `Args`
 :   compatible types to create a `basic_json` object
 
+## Iterator invalidation
+
+For [`ordered_json`](../ordered_json.md), adding a value to an object can yield a reallocation, in which case all
+iterators (including the `end()` iterator) and all references to the elements are invalidated.
+
 ## Parameters
 
 `args` (in)