docs: add missing dependency to install instructions (#35)

Author: GregoryConrad

README.md

@@ -20,7 +20,7 @@ Rust support for Dart's Native Assets.
 ## Getting Started
 1. Install [rustup](https://rustup.rs), for Rust, on your development computer
    (if you are a library author, consumers of your package will have to do the same)
-2. Run `flutter pub add native_toolchain_rs` for Flutter or `dart pub add native_toolchain_rs` for Dart-only
+2. Run `flutter pub add native_toolchain_rs hooks` for Flutter or `dart pub add native_toolchain_rs hooks` for Dart-only
 3. (Until [Native Assets](https://github.com/dart-lang/sdk/issues/50565) is fully released) Switch to Flutter's beta channel: `flutter channel beta`
 4. See [Code Setup](#code-setup)