Add license link to README.

Author: OlgaMaciaszek

docs/src/main/asciidoc/README.adoc

@@ -19,3 +19,7 @@ include::https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/maste
 == Contributing
 
 include::https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/master/docs/src/main/asciidoc/contributing.adoc[]
+
+== License
+
+The project license file is available https://raw.githubusercontent.com/spring-cloud/spring-cloud-openfeign/2.2.x/LICENSE.txt[here].