docs(README): add LICENSE section (#7327)

README.md

@@ -90,3 +90,9 @@ To help with the migration, here are the currently known issues with 3.X. This l
 ## Security contact
 
 Please disclose any security-related issues or vulnerabilities by emailing [[email protected]](mailto:[email protected]), instead of using the public issue tracker.
+
+## License
+
+SwaggerUI is licensed under [Apache 2.0 license](https://github.com/swagger-api/swagger-ui/blob/master/LICENSE).
+SwaggerUI comes with an explicit [NOTICE](https://github.com/swagger-api/swagger-ui/blob/master/NOTICE) file
+containing additional legal notices and information.