feat: definePlugin helper (#2302)

* feat: add definePlugin

* chore: changeset

* fix: export helper

Author: so1ve

.changeset/honest-yaks-tan.md

@@ -0,0 +1,5 @@
+---
+"@rspack/cli": patch
+---
+
+add definePlugin helper

packages/rspack-cli/src/index.ts

@@ -1,2 +1,2 @@
 export * from "./types";
-export { RspackCLI, defineConfig } from "./rspack-cli";
+export { RspackCLI, defineConfig, definePlugin } from "./rspack-cli";

packages/rspack-cli/src/rspack-cli.ts

@@ -16,6 +16,7 @@ import {
 import { normalizeEnv } from "./utils/options";
 import { loadRspackConfig } from "./utils/loadConfig";
 import { Mode } from "@rspack/core/src/config";
+import { RspackPluginInstance, RspackPluginFunction } from "@rspack/core";
 
 type RspackEnv = "development" | "production";
 export class RspackCLI {
@@ -252,3 +253,10 @@ export class RspackCLI {
 export function defineConfig(config: RspackOptions): RspackOptions {
 	return config;
 }
+
+// Note: use union type will make apply function's `compiler` type to be `any`
+export function definePlugin(plugin: RspackPluginFunction): RspackPluginFunction
+export function definePlugin(plugin: RspackPluginInstance): RspackPluginInstance
+export function definePlugin(plugin: any): any {
+	return plugin;
+}