update changelog

CHANGELOG.md

@@ -3,6 +3,7 @@ All notable changes to this project will be documented in this file.
 This project uses the changelog in accordance with [keepchangelog](http://keepachangelog.com/). Please use this to write notable changes, which is not the same as git commit log...
 
 ## [unreleased][unreleased]
+- Changed `hf mf c*` - now accepts a --gdm flag to write using uscuid/gdm 20/23 alt magic wakeup (@nvx)
 - Changed `pm3_console()` - Python/Lua/C: replace `passthru` by `capture` and `quiet` (@doegox)
 - Fixed `hf iclass list` - annotation crc handled better (@iceman1001)
 - Fixed `hf_mf_uscuid_prog.lua` - bad divisions and code style fixes (@iceman1001)