deduction guides for std::ranges::join_view

From cppreference.com
< cpp‎ | ranges‎ | join view
Ranges library
Range adaptors
template < class R>
explicit join_view(R&& ) - > join_view< views::all_t <R>> ;
(since C++20)

The deduction guide is provided for std::ranges::join_view to allow deduction from range

Example