Add third party notices -- copied from chakracore

NOTICE.txt

@@ -0,0 +1,46 @@
+vcpkg uses third party material from the projects listed below.
+The original copyright notice and the license under which Microsoft
+received such third party material are set forth below. Microsoft
+reserves all other rights not expressly granted, whether by
+implication, estoppel or otherwise.
+
+In the event that we accidentally failed to list a required notice, please
+bring it to our attention by posting an issue.
+
+THIRD-PARTY SOFTWARE NOTICES AND INFORMATION
+Do Not Translate or Localize
+
+vcpkg incorporates third party material from the projects listed below.
+The original copyright notice and the license under which Microsoft received
+such third party materials are set forth below. Microsoft reserved all other
+rights not expressly granted, whether by implication, estoppel or otherwise.
+
+1.  Catch2
+
+%% Catch2 NOTICES, INFORMATION, AND LICENSE BEGIN HERE
+=========================================
+Boost Software License - Version 1.0 - August 17th, 2003
+
+Permission is hereby granted, free of charge, to any person or organization
+obtaining a copy of the software and accompanying documentation covered by
+this license (the "Software") to use, reproduce, display, distribute,
+execute, and transmit the Software, and to prepare derivative works of the
+Software, and to permit third-parties to whom the Software is furnished to
+do so, all subject to the following:
+
+The copyright notices in the Software and this entire statement, including
+the above license grant, this restriction and the following disclaimer,
+must be included in all copies of the Software, in whole or in part, and
+all derivative works of the Software, unless such copies or derivative
+works are solely in the form of machine-executable object code generated by
+a source language processor.
+
+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, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
+=========================================
+END OF Catch2 NOTICES, INFORMATION, AND LICENSE