[Bug libstdc++/101268] New: Refer manual readers to cppreference.com for API details

[giecrilj at stegny dot 2a.pl]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101268

            Bug ID: 101268
           Summary: Refer manual readers to cppreference.com for API
                    details
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: giecrilj at stegny dot 2a.pl
  Target Milestone: ---

Since we have given up on documenting all standard library features we have
implemented (I mean patches are not welcome), we should add a reference to
cppreference.com to the product manual.