Overwork documentation (#4516)

docs/mkdocs/docs/api/basic_json/index.md

@@ -42,7 +42,15 @@ class basic_json;
 
 ## Iterator invalidation
 
-Todo
+All operations that add values to an **array** ([`push_back`](push_back.md) , [`operator+=`](operator+=.md),
+[`emplace_back`](emplace_back.md), [`insert`](insert.md), and [`operator[]`](operator%5B%5D.md) for a non-existing
+index) can yield a reallocation, in which case all iterators (including the [`end()`](end.md) iterator) and all
+references to the elements are invalidated.
+
+For [`ordered_json`](../ordered_json.md), also all operations that add a value to an **object**
+([`push_back`](push_back.md), [`operator+=`](operator+=.md), [`emplace`](emplace.md), [`insert`](insert.md),
+[`update`](update.md), and [`operator[]`](operator%5B%5D.md) for a non-existing key) can yield a reallocation, in
+which case all iterators (including the [`end()`](end.md) iterator) and all references to the elements are invalidated.
 
 ## Requirements