update docs and add contributor

CHANGES.md

@@ -2,7 +2,7 @@
 
 ## 3.5.9-RC
 
-* 
+* Fix: Editing table with Spreadsheet like GUI (Handsontable) is failed
 
 ## 3.5.8
 

src/client/js/components/StaffCredit/Contributor.js

@@ -70,6 +70,7 @@ const contributors = [
           { name: 'kmyk' },
           { name: 'aximov' },
           { name: 'tats-u' },
+          { name: 'yamatomo717' },
         ],
       },
     ],