codemod: update license section in README

Summary: Make it clear that different parts of the code base have different licenses.

Reviewed By: lmvasquezg

Differential Revision: D65717051

fbshipit-source-id: 236d95e64931227d7910b9d72bc9e34427a2d2d6

Author: quark-zju

README.md

@@ -72,4 +72,8 @@ You can [Report an Issue on GitHub](https://github.com/facebook/sapling/issues)
 
 # License
 
-See [LICENSE](LICENSE).
+The main project is licensed under [GPL-2.0](LICENSE).
+
+The [website](website) and [ISL](addons) are licensed under [MIT](addons/LICENSE).
+
+Library subprojects, such as [minibytes](eden/scm/lib/minibytes), might have different licenses. Please refer to the `LICENSE` file and source code headers in each library for detailed information.

website/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) Meta Platforms, Inc. and its affiliates.
+
+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.