Add initial project files (excluding ignored content)

external/spdlog/fwd.h

@@ -0,0 +1,18 @@
+// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+
+#pragma once
+
+namespace spdlog {
+class logger;
+class formatter;
+
+namespace sinks {
+class sink;
+}
+
+namespace level {
+enum level_enum : int;
+}
+
+}  // namespace spdlog