Reference README.md from localized versions

Mention that the README.md is the only one being up-to-date.

README.ko.md

@@ -1,3 +1,5 @@
+_Only the original [README](README.md) is guaranteed to be up-to-date._
+
 # scrcpy (v1.11)
 
 This document will be updated frequently along with the original Readme file

README.pt-br.md

@@ -1,3 +1,5 @@
+_Only the original [README](README.md) is guaranteed to be up-to-date._
+
 # scrcpy (v1.12.1)
 
 Esta aplicação fornece visualização e controle de dispositivos Android conectados via