Re-add the top level LICENSE file (#37916)

Summary:
Pull Request resolved: #37916

Repos on GitHub should have a top level LICENSE file to make sure GitHub can autodiscover
the correct license for the project.

Once we moved the file inside packages/react-native/ the autodiscovery is not working anymore (it returns a 404).

Changelog:
[Internal] - Re-add the top level LICENSE file

Reviewed By: hoxyq

Differential Revision: D46764347

fbshipit-source-id: cd760c004cf97248490b43f7ba08a47ef2d23c89

LICENSE

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

README.md

@@ -143,5 +143,5 @@ React Native is MIT licensed, as found in the [LICENSE][l] file.
 
 React Native documentation is Creative Commons licensed, as found in the [LICENSE-docs][ld] file.
 
-[l]: https://github.com/facebook/react-native/blob/main/packages/react-native/LICENSE
-[ld]: https://github.com/facebook/react-native/blob/HEAD/LICENSE-docs
+[l]: https://github.com/facebook/react-native/blob/main/LICENSE
+[ld]: https://github.com/facebook/react-native/blob/main/LICENSE-docs