fetch following contacts if we are missing any

Signed-off-by: William Casarin <jb55@jb55.com>

damus/Util/InsertSort.swift

@@ -18,6 +18,26 @@ func insert_uniq<T: Equatable>(xs: inout [T], new_x: T) -> Bool {
     return true
 }
 
+func insert_uniq_by_pubkey(events: inout [NostrEvent], new_ev: NostrEvent, cmp: (NostrEvent, NostrEvent) -> Bool) -> Bool {
+    var i: Int = 0
+    
+    for event in events {
+        // don't insert duplicate events
+        if new_ev.pubkey == event.pubkey {
+            return false
+        }
+        
+        if cmp(new_ev, event) {
+            events.insert(new_ev, at: i)
+            return true
+        }
+        i += 1
+    }
+    
+    events.append(new_ev)
+    return true
+}
+
 func insert_uniq_sorted_event(events: inout [NostrEvent], new_ev: NostrEvent, cmp: (NostrEvent, NostrEvent) -> Bool) -> Bool {
     var i: Int = 0