Added Third Party Notices document

THIRD-PARTY-NOTICES.TXT

@@ -0,0 +1,52 @@
+Six Labors' Shared Infrastructure uses third-party libraries or other resources that may be
+distributed under licenses different than the Shared Infrastructure itself.
+
+In the event that we accidentally failed to list a required notice, please
+bring it to our attention by posting an issue.
+
+The attached notices are provided for information only.
+
+
+License notice for HashCode
+-----
+
+Licensed to the .NET Foundation under one or more agreements.
+The .NET Foundation licenses this file to you under the MIT license.
+See the LICENSE file in the CoreFX project root for more information.
+
+https://github.com/dotnet/corefx/blob/e99ec129cfd594d53f4390bf97d1d736cff6f860/LICENSE.TXT
+https://github.com/dotnet/corefx/blob/e99ec129cfd594d53f4390bf97d1d736cff6f860/src/Common/src/CoreLib/System/HashCode.cs
+
+The xxHash32 implementation is based on the code published by Yann Collet:
+https://raw.githubusercontent.com/Cyan4973/xxHash/5c174cfa4e45a42f94082dc0d4539b39696afea1/xxhash.c
+  xxHash - Fast Hash algorithm
+  Copyright (C) 2012-2016, Yann Collet
+  
+  BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
+  
+  Redistribution and use in source and binary forms, with or without
+  modification, are permitted provided that the following conditions are
+  met:
+  
+  * Redistributions of source code must retain the above copyright
+  notice, this list of conditions and the following disclaimer.
+  * Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the following disclaimer
+  in the documentation and/or other materials provided with the
+  distribution.
+  
+  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+  OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+  
+  You can contact the author at :
+  - xxHash homepage: http://www.xxhash.com
+  - xxHash source repository : https://github.com/Cyan4973/xxHash