[libc++][ranges] Implement `ranges::nth_element`.

Differential Revision: https://reviews.llvm.org/D128149

NOKEYCHECK=True
GitOrigin-RevId: 23c7328bad927c2ec4d1ecf37fc07b4475f68a76
diff --git a/include/module.modulemap.in b/include/module.modulemap.in
index 98bb00b..0447cf0 100644
--- a/include/module.modulemap.in
+++ b/include/module.modulemap.in
@@ -342,6 +342,7 @@
       module ranges_move                     { private header "__algorithm/ranges_move.h" }
       module ranges_move_backward            { private header "__algorithm/ranges_move_backward.h" }
       module ranges_none_of                  { private header "__algorithm/ranges_none_of.h" }
+      module ranges_nth_element              { private header "__algorithm/ranges_nth_element.h" }
       module ranges_remove                   { private header "__algorithm/ranges_remove.h" }
       module ranges_remove_if                { private header "__algorithm/ranges_remove_if.h" }
       module ranges_replace                  { private header "__algorithm/ranges_replace.h" }