commands: split response tokenizer into separate file

src/commands/queue/add.rs

@@ -1,12 +1,10 @@
 use serde::{Deserialize, Serialize};
 
 use crate::{
-    request_tokenizer::RequestTokenizer,
-    commands::{
-        Command, Request, RequestParserError, RequestParserResult, ResponseAttributes,
-        ResponseParserError,
-    },
+    commands::{Command, Request, RequestParserError, RequestParserResult, ResponseParserError},
     common::{SongPosition, Uri},
+    request_tokenizer::RequestTokenizer,
+    response_tokenizer::ResponseAttributes,
 };
 
 pub struct Add;