update README

Author: panki27

README.md

@@ -9,6 +9,7 @@ This is a Minesweeper implementation for the Flipper Zero device.
 - Arrow buttons to move
 - Push center button to open field
 - Hold center button to toggle flag
+- Push center button on an already open field that has the correct amount of flags surrounding it to auto-open the remaining ones (thanks @gelin!)
 
 ## Compiling