Add an element to the end.

Insert a new element at the end of the container. (1) copy-constructs the new element from jv, (2) move-constructs from jv.

If capacity() < size() + 1, a reallocation occurs first, and all iterators and references are invalidated. Any past-the-end iterators are always invalidated.

The new element will be constructed using the container’s associated boost::container::pmr::memory_resource.

Amortized constant.

Strong guarantee. Calls to memory_resource::allocate may throw.