fix(package): add packageManager field for pnpm

Add `packageManager` field to package.json to specify pnpm version.
This is required by pnpm-action-setup when using socket-registry actions
that don't specify the pnpm version explicitly.

See: https://pnpm.io/package_json#packagemanager

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: jdalton

package.json

@@ -1,6 +1,7 @@
 {
   "name": "@socketregistry/packageurl-js",
   "version": "1.3.5",
+  "packageManager": "pnpm@>=10.21.0",
   "license": "MIT",
   "description": "Socket.dev optimized package override for packageurl-js",
   "keywords": [