add LICENSE file

LICENSE

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+Microsoft Reference Source License (Ms-RSL)
+===========================================
+
+This license governs use of the accompanying software. If you use the software,
+you accept this license. If you do not accept the license, do not use the
+software.
+
+1. Definitions
+--------------
+
+The terms "reproduce", "reproduction" and "distribution" have the same meaning
+here as under U.S. copyright law.
+
+"You" means the licensee of the software.
+
+"Your company" means the company you worked for when you downloaded the
+software.
+
+"Reference use" means use of the software within your company as a reference, in
+read only form, for the sole purposes of debugging your products, maintaining
+your products, or enhancing the interoperability of your products with the
+software, and specifically excludes the right to distribute the software outside
+of your company.
+
+Licensed patents" means any Licensor patent claims which read directly on the
+software as distributed by the Licensor under this license.
+
+2. Grant of Rights
+------------------
+
+(A) Copyright Grant - Subject to the terms of this license, the Licensor grants
+you a non-transferable, non-exclusive, worldwide, royalty-free copyright license
+to reproduce the software for reference use.
+
+(B) Patent Grant - Subject to the terms of this license, the Licensor grants you
+a non-transferable, non-exclusive, worldwide, royalty-free patent license under
+licensed patents for reference use.
+
+3. Limitations
+--------------
+
+(A) No Trademark License - This license does not grant you any rights to use the
+Licensor's name, logo, or trademarks.
+
+(B) If you begin patent litigation against the Licensor over patents that you
+think may apply to the software (including a cross-claim or counterclaim in a
+lawsuit), your license to the software ends automatically.
+
+(C) The software is licensed "as-is." You bear the risk of using it. The
+Licensor gives no express warranties, guarantees or conditions. You may have
+additional consumer rights under your local laws which this license cannot
+change. To the extent permitted under your local laws, the Licensor excludes the
+implied warranties of merchantability, fitness for a particular purpose and
+non-infringement.