feat(cli): support reading JavaScript from piped stdin

cli/README.md

@@ -32,6 +32,14 @@ Or if you'd like to use Boa's REPL, simply type:
     boa
 ```
 
+You can also pipe JavaScript into Boa:
+
+```shell
+    echo 'console.log(1 + 2)' | boa
+    cat script.js | boa
+    boa < script.js
+```
+
 ## CLI Options
 
 ```txt

cli/src/main.rs

@@ -44,7 +44,7 @@ use std::{
     cell::RefCell,
     collections::VecDeque,
     fs::OpenOptions,
-    io,
+    io::{self, IsTerminal, Read},
     path::{Path, PathBuf},
     rc::Rc,
     thread,
@@ -571,6 +571,16 @@ fn main() -> Result<()> {
     } else if let Some(ref expr) = args.expression {
         evaluate_expr(expr, &args, &mut context, &printer)?;
         return Ok(());
+    } else if !io::stdin().is_terminal() {
+        let mut input = String::new();
+        io::stdin()
+            .read_to_string(&mut input)
+            .wrap_err("failed to read stdin")?;
+        return if input.is_empty() {
+            Ok(())
+        } else {
+            evaluate_expr(&input, &args, &mut context, &printer)
+        };
     }
 
     let handle = start_readline_thread(sender, printer.clone(), args.vi_mode);