Add support for Boxed Error

[Murasame233]

error[E0308]: mismatched types
   --> src/main.rs:?:?
    |
?   |         self.client.get(url).send().await
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `Result<Response, Box<dyn Error>>`, found `Result<Response, Error>`
    |
    = note: expected enum `Result<_, Box<(dyn StdError + 'static)>>`
               found enum `Result<_, reqwest_middleware::Error>`