:+1: version and update docs

CHANGES.md

@@ -16,6 +16,7 @@ Upgrading Guide: https://docs.growi.org/en/admin-guide/upgrading/36x.html
 
 ## 3.5.21
 
+* Improvement: Cache control when retrieving attachment data
 * Fix: Inviting user doesn't work
     * Introduced by 3.5.20
 

package.json

@@ -1,6 +1,6 @@
 {
   "name": "growi",
-  "version": "3.5.21-RC",
+  "version": "3.6.0-RC",
   "description": "Team collaboration software using markdown",
   "tags": [
     "wiki",