Add breaking changes to doc (it's sort of breaking in that behaviour is changing)

Author: mcarans

documentation/index.md

@@ -54,6 +54,10 @@ The library has detailed API documentation which can be found in the menu at the
 
 
 ## Breaking Changes
+From 6.5.0, files will not be uploaded to the HDX filestore if the hash and size have 
+not changed, but if there are any resource metadata changes, except for last_modified, 
+they will still take place).
+
 From 6.4.5, fix for changes in dependency defopt 7.0.0
 
 From 6.2.8, fix mark_data_updated which was broken due to an error in