[fmt] added rustfmt.toml and applied it

rustfmt.toml

@@ -0,0 +1,3 @@
+group_imports = "StdExternalCrate"
+imports_granularity = "Crate"
+imports_layout = "HorizontalVertical"

src/main.rs

@@ -1,9 +1,10 @@
-use actix_web::{App, HttpServer};
-use std::env;
-use std::net::IpAddr;
-use std::net::SocketAddr;
-use std::thread::available_parallelism;
+use std::{
+    env,
+    net::{IpAddr, SocketAddr},
+    thread::available_parallelism,
+};
 
+use actix_web::{App, HttpServer};
 use clap::{crate_name, crate_version, Parser};
 
 #[derive(Parser, Debug)]