Feat: Use clap for argument parsing.

src/main.rs

@@ -1,16 +1,14 @@
+use clap::Parser;
+
+// Search for a pattern in a file and display the lines that contain it.
+#[derive(Parser)]
 struct Cli {
     pattern: String,
     path: std::path::PathBuf,
 }
 
 fn main() {
-    let pattern = std::env::args().nth(1).expect("no pattern given.");
-    let path = std::env::args().nth(2).expect("no path given.");
-
-    let args = Cli {
-        pattern,
-        path: std::path::PathBuf::from(path),
-    };
+    let args = Cli::parse();
 
     println!("pattern: {:?}, path: {:?}", args.pattern, args.path)
 }