Feat: use anyhow for error reporting.

I don't think that the error will properly be reported due to only printing
lines that match the pattern.

src/main.rs

@@ -1,3 +1,4 @@
+use anyhow::{Context, Result};
 use clap::Parser;
 
 // Search for a pattern in a file and display the lines that contain it.
@@ -7,16 +8,14 @@ struct Cli {
     path: std::path::PathBuf,
 }
 
-#[derive(Debug)]
-struct CustomError(String);
-
-fn main() -> Result<(), CustomError> {
+fn main() -> Result<()> {
     let args = Cli::parse();
 
     // let content = std::fs::read_to_string(&args.path).expect("Could not read file.");
 
     let content = std::fs::read_to_string(&args.path)
-        .map_err(|err| CustomError(format!("Error reading `{}`: {}", args.path.display(), err)))?;
+        .with_context(|| format!("could not read file `{}`.", args.path.display()))?;
+
 
     for line in content.lines() {
         if line.contains(&args.pattern) {