Prepare snapshot version 2.21.1-SNAPSHOT (#785)

Co-authored-by: davidliu <242400+davidliu@users.noreply.github.com>

Author: davidliu

gradle.properties

@@ -23,7 +23,7 @@ kotlin.code.style=official
 ###############################################################
 
 GROUP=io.livekit
-VERSION_NAME=2.21.0
+VERSION_NAME=2.21.1-SNAPSHOT
 
 POM_DESCRIPTION=LiveKit Android SDK, WebRTC Rooms