docs(Readme.md): Add license line

Adding same license to rxjs-docs as exists in RxJs

none

Author: Jennifer Luker

README.md

@@ -5,7 +5,9 @@
 # rxjs-docs
 The home for new work on the new RxJS docs (RxJS v5 and up)
 
+License is the same as the RxJS project: https://github.com/reactivex/rxjs
 
+[Apache 2.0 License](LICENSE.txt)
 - [Code of Conduct](CODE_OF_CONDUCT.md)
 - [Contribution Guidelines](CONTRIBUTING.md)
 
@@ -19,4 +21,4 @@ Run `ng build` to build the project. The build artifacts will be stored in the `
 
 ## License
 
-License is the same as the RxJS project: https://github.com/reactivex/rxjs
+