Update README with PackageManager type and usage

Added PackageManager to the Module type and provided an example of requiring it using global.require. This clarifies usage for developers integrating package management functionality.

Author: DerGoogler

README.md

@@ -45,7 +45,7 @@ Here's an example of what your `config.json` file should look like:
 [Types Folder](./types)
 
 ```ts
-type Module = FileSystem | Reflect | Process | Module;
+type Module = FileSystem | Reflect | Process | Module | PackageManager;
 
 interface Global {
   require(module: string): Module | null;
@@ -58,4 +58,5 @@ const fs: FileSystem = global.require("wx:fs");
 const reflect: Reflect = global.require("wx:reflect");
 const process: Process = global.require("wx:process");
 const module: Module = global.require("wx:module");
+const pm: PackageManager = global.require("wx:pm");
 ```