Refactor packet string charset

src/main/java/net/packet/Packet.java

@@ -1,5 +1,10 @@
 package net.packet;
 
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
+
 public interface Packet {
+    Charset STRING_CHARSET = StandardCharsets.US_ASCII;
+
     byte[] getBytes();
 }