Censor unclebobmartin from damus

Limits the size of posts viewable within damus to 32,000 bytes. It's
still probably too big, but let's have some sane limit so uncle's named
bob can't break your app just because they can.

Changelog-Fixed: Limit post sizes to max 32,000 as an upper bound sanity limit.
Signed-off-by: William Casarin <jb55@jb55.com>

damus/Models/ThreadModel.swift

@@ -148,6 +148,10 @@ class ThreadModel: ObservableObject {
     }
     
     func add_event(_ ev: NostrEvent, privkey: String?) {
+        guard ev.should_show_event else {
+            return
+        }
+        
         if event_map[ev.id] != nil {
             return
         }