include the otel header-only part directly for ease of use

ext/opentelemetry-cpp-api-only/include/opentelemetry/std/string_view.h

@@ -0,0 +1,21 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+#pragma once
+
+// IWYU pragma: private, include "opentelemetry/nostd/string_view.h"
+
+#include <string_view>
+
+#include "opentelemetry/version.h"
+
+OPENTELEMETRY_BEGIN_NAMESPACE
+// Standard Type aliases in nostd namespace
+namespace nostd
+{
+
+// nostd::string_view
+using string_view = std::string_view;
+
+}  // namespace nostd
+OPENTELEMETRY_END_NAMESPACE