Updated TODO.

TODO.md

@@ -28,6 +28,8 @@ Implement "FEP-3b86: Activity Intents" https://codeberg.org/fediverse/fep/src/br
 
 Track "FEP-ef61: Portable Objects" https://codeberg.org/fediverse/fep/src/branch/main/fep/ef61/fep-ef61.md
 
+Track "Public Key Directory Server Specification" https://publickey.directory/
+
 Integrate "Added handling for International Domain Names" PR https://codeberg.org/grunfink/snac2/pulls/104
 
 The 'history' pages are just monthly HTML snapshots of the local timeline. This is ok and cheap and easy, but is problematic if you e.g. intentionally delete a post because it will remain there in the history forever. If you activate local timeline purging, purged entries will remain in the history as 'ghosts', which may or may not be what the user wants.