build: add packageManager

Author: John Campion

demo/package.json

@@ -1,7 +1,7 @@
 {
   "name": "tw-plugin-demo",
   "private": true,
-  "packageManager": "^pnpm@8.0.0",
+  "packageManager": "^pnpm@8.1.0",
   "version": "0.0.0",
   "type": "module",
   "scripts": {

package.json

@@ -3,7 +3,7 @@
   "version": "0.1.0",
   "description": "An updated animation plugin for Tailwind CSS v3",
   "main": "dist/index.js",
-  "packageManager": "^pnpm@8.0.0",
+  "packageManager": "^pnpm@8.1.0",
   "scripts": {
     "dev": "tsc --watch & cd ./demo && npm run-script dev",
     "build": "tsc",