[clang] [libc++] Implement ranges::contains (PR #65148)

[Konstantin Varlamov via cfe-commits]

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@@ -0,0 +1,190 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <algorithm>
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
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var-const wrote:

Nit: please add a blank line after this line (to separate the `UNSUPPORTED` annotations from the synopsis).

https://github.com/llvm/llvm-project/pull/65148