docs: update readme

Author: dingyi222666

README.md

@@ -13,6 +13,10 @@ A Lua 5.3 Lexer & Parser written in pure Kotlin.
 
 ## Usage
 
+Now the project isn't publish to maven central, so you need to clone and build it by yourself.
+
+In the future, we will publish it to maven central.
+
 ```kotlin
 val lexer = LuaLexer(source)
 val parser = LuaParser()