chore: add how to use on main

Author: arferreira

src/main.rs

@@ -1,3 +1,14 @@
+use cipher_blend::{decrypt, encrypt};
+
 fn main() {
-    println!("Cipher Blend");
+    let original_message = "Hello, Rust!";
+    let shift = 3;
+
+    // Encrypt
+    let encrypted_message = encrypt(original_message, shift);
+    println!("Encrypted: {}", encrypted_message);
+
+    // Decrypt
+    let decrypted_message = decrypt(&encrypted_message, shift);
+    println!("Decrypted: {}", decrypted_message);
 }