[zlib] Add LICENSE, update README

vendor/README.md

@@ -141,4 +141,11 @@ Includes full bindings as well as wrappers to match the `core:crypto` API.
 [CMark](https://github.com/commonmark/cmark) CommonMark parsing library.
 
 See also LICENSE in the `commonmark` directory itself.
-Includes full bindings and Windows `.lib` and `.dll`.
+Includes full bindings and Windows `.lib` and `.dll`.
+
+## CommonMark
+
+[zlib](https://github.com/madler/zlib) data compression library
+
+See also LICENSE in the `zlib` directory itself.
+Includes full bindings.

vendor/zlib/LICENSE

@@ -0,0 +1,20 @@
+ (C) 1995-2022 Jean-loup Gailly and Mark Adler
+
+  This software is provided 'as-is', without any express or implied
+  warranty.  In no event will the authors be held liable for any damages
+  arising from the use of this software.
+
+  Permission is granted to anyone to use this software for any purpose,
+  including commercial applications, and to alter it and redistribute it
+  freely, subject to the following restrictions:
+
+  1. The origin of this software must not be misrepresented; you must not
+     claim that you wrote the original software. If you use this software
+     in a product, an acknowledgment in the product documentation would be
+     appreciated but is not required.
+  2. Altered source versions must be plainly marked as such, and must not be
+     misrepresented as being the original software.
+  3. This notice may not be removed or altered from any source distribution.
+
+  Jean-loup Gailly        Mark Adler
+  [email protected]          [email protected]