Add `-n` option to echo

Created by: polymetric1

src/bin/echo.rs

 use std::env;
 
 fn main() {
+    let mut newline = true;
     for arg in env::args().skip(1) {
+        if arg == "-n" {
+            newline = false
+            continue;
+        }
         print!("{} ", arg);
     }
-    print!("\n");
+    if newline {
+        print!("\n");
+    }
 }