created sinks fmt and details folders in src

src/details/periodic_worker.cpp

@@ -0,0 +1,26 @@
+// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+
+#pragma once
+
+#    include <spdlog/details/periodic_worker.h>
+
+namespace spdlog {
+namespace details {
+
+// stop the worker thread and join it
+ periodic_worker::~periodic_worker()
+{
+    if (worker_thread_.joinable())
+    {
+        {
+            std::lock_guard<std::mutex> lock(mutex_);
+            active_ = false;
+        }
+        cv_.notify_one();
+        worker_thread_.join();
+    }
+}
+
+} // namespace details
+} // namespace spdlog