NIP-02, NIP-51: new tags should be added to the end of the list

Fixes #958

02.md

@@ -27,6 +27,8 @@ For example:
 
 Every new following list that gets published overwrites the past ones, so it should contain all entries. Relays and clients SHOULD delete past following lists as soon as they receive a new one.
 
+Whenever new follows are added to an existing list, clients SHOULD append them to the end of the list, so they are stored in chronological order.
+
 ## Uses
 
 ### Follow list backup

51.md

@@ -10,6 +10,8 @@ This NIP defines lists of things that users can create. Lists can contain refere
 
 Public items in a list are specified in the event `tags` array, while private items are specified in a JSON array that mimics the structure of the event `tags` array, but stringified and encrypted using the same scheme from [NIP-04](04.md) (the shared key is computed using the author's public and private key) and stored in the `.content`.
 
+When new items are added to an existing list, clients SHOULD append them to the end of the list, so they are stored in chronological order.
+
 ## Types of lists
 
 ## Standard lists