fix: Fix clippy warnings

- Use is_empty iso len() == 0
- Remove unneeded return type

src/main.rs

@@ -10,7 +10,7 @@ struct Args {
     script: Option<String>,
 }
 
-fn run(lines: io::Lines<io::BufReader<File>>) -> () {
+fn run(lines: io::Lines<io::BufReader<File>>) {
     for line in lines {
         println!("Line: {}", line.unwrap());
     }
@@ -30,7 +30,7 @@ fn run_prompt() -> Result<(), io::Error> {
 
         let mut buffer = String::new();
         io::stdin().read_line(&mut buffer)?;
-        if buffer.len() == 0 {
+        if buffer.is_empty() {
             break;
         }
         println!("input: '{}', {}", buffer, buffer.len());