add modification notice to readme

Author: parkan

README.md

@@ -1,5 +1,7 @@
 # FUTO Keyboard
 
+> **Modified version.** This is a personal fork of [FUTO Keyboard](https://github.com/futo-org/android-keyboard), modified by Arkadiy Kukarkin (parkan). Changes include transformer decoder fixes (beam search scoring, context window, suggestion timeout). Not affiliated with or endorsed by FUTO; for the official keyboard see [keyboard.futo.org](https://keyboard.futo.org/).
+
 The goal is to make a good modern keyboard that stays offline and doesn't spy on you. This keyboard is a fork of [LatinIME, The Android Open-Source Keyboard](https://android.googlesource.com/platform/packages/inputmethods/LatinIME), with significant changes made to it.
 
 Check out the [FUTO Keyboard website](https://keyboard.futo.org/) for downloads and more information.