Add CHANGELOG entry for N3 patches (#516).

Author: RubenVerborgh

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## 4.0.0
 - OIDC is now supported as authentication method in addition to WebID-TLS.
 - Both Node.js 6 and 8 are now supported.
+- The server now accepts N3 patches.
 - Responses now contain a WAC-Allow header, listing the access permissions
   for the current user and non-authenticated users.
 - The `authProxy` configuration parameter has been added,