feat: add native plugin example (#262)

crates/rolldown_plugin_hello/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name                 = "rolldown_plugin_hello"
+version              = "0.1.0"
+edition.workspace    = true
+homepage.workspace   = true
+license.workspace    = true
+repository.workspace = true
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+rolldown    = { path = "../rolldown" }
+async-trait = { workspace = true }

crates/rolldown_plugin_hello/src/lib.rs

@@ -0,0 +1,19 @@
+use std::borrow::Cow;
+
+use rolldown::{HookNoopReturn, Plugin, PluginContext};
+
+#[derive(Debug)]
+pub struct HelloPlugin;
+
+#[async_trait::async_trait]
+impl Plugin for HelloPlugin {
+  fn name(&self) -> Cow<'static, str> {
+    "hello".into()
+  }
+
+  #[allow(clippy::print_stdout)]
+  async fn build_start(&self, _ctx: &mut PluginContext) -> HookNoopReturn {
+    println!("hello");
+    Ok(())
+  }
+}