Added stored_size option to small_vector

doc/container.qbk

@@ -803,6 +803,12 @@ the last template parameter and defined using the utility class
    [classref boost::container::growth_factor_60 growth_factor_60] and
    [classref boost::container::growth_factor_50 growth_factor_100].
 
+*  [classref boost::container::stored_size stored_size]: the type that will be used to store size-related
+   parameters inside of the vector. Sometimes, when the maximum capacity to be used is much less than the
+   theoretical maximum that a vector can hold, it's interesting to use smaller unsigned integer types to represent
+   `size()` and `capacity()` inside vector, so that the size of an empty vector is minimized and cache 
+   performance might be improved. See [classref boost::container::stored_size stored_size] for more details.
+
 See the following example to see how [classref boost::container::small_vector_options small_vector_options] can be
 used to customize `small_vector`:
 
@@ -1417,7 +1423,9 @@ use [*Boost.Container]? There are several reasons for that:
 
 [section:release_notes_boost_1_87_00 Boost 1.87 Release]
 
-* Added [classref boost::container::stored_size stored_size] option to [classref boost::container::static_vector static_vector].
+* Added [classref boost::container::stored_size stored_size] option to
+  [classref boost::container::static_vector static_vector] and
+  [classref boost::container::small_vector small_vector].
 
 * Fixed bugs/issues:
    * [@https://github.com/boostorg/container/issues/261 GitHub #261: ['"End iterators are not dereferencable"]].