Update the third-party dependencies list for release 2.1.0-beta.1.

Add sdplog library.

Author: djova-dolby

third_party_license_src.md

@@ -1936,3 +1936,42 @@ ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 DEALINGS IN THE SOFTWARE.
 ```
 
+## spdlog
+
+### Source root
+
+https://github.com/gabime/spdlog/tree/b75edfafca581e33be29ab51b9546b2e955c2853
+
+### License URL
+
+https://github.com/gabime/spdlog/tree/b75edfafca581e33be29ab51b9546b2e955c2853/LICENSE
+
+### License
+
+```
+The MIT License (MIT)
+
+Copyright (c) 2016 Gabi Melman.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+
+-- NOTE: Third party dependency used by this software --
+This software depends on the fmt lib (MIT License),
+and users must comply to its license: https://github.com/fmtlib/fmt/blob/master/LICENSE.rst
+```