doc: generate use page in javadoc

diff --git a/build.gradle b/build.gradle
index 54a4c94..6316c5f 100644
--- a/build.gradle
+++ b/build.gradle
@@ -78,6 +78,7 @@
 
     javadoc.options {
         encoding = 'UTF-8'
+        use = true
         links 'https://docs.oracle.com/javase/8/docs/api/'
     }