feat: support isPluginExists for plugin manager (#6702)

Author: caohuilin

.changeset/modern-bulldogs-cross.md

@@ -0,0 +1,7 @@
+---
+'@modern-js/plugin-v2': patch
+---
+
+feat: support isPluginExists for plugin manager
+
+feat: 插件支持 isPluginExists 方法

packages/toolkit/plugin-v2/src/manager.ts

@@ -171,5 +171,6 @@ export function createPluginManager(): PluginManager {
     getPlugins,
     addPlugins,
     clear,
+    isPluginExists: (name: string) => plugins.has(name),
   };
 }

packages/toolkit/plugin-v2/src/types/plugin.ts

@@ -48,4 +48,5 @@ export type PluginManager = {
   getPlugins: () => Plugin[];
   addPlugins: (plugins: Array<Plugin | Falsy>) => void;
   clear: () => void;
+  isPluginExists: (name: string) => boolean;
 };