kick off action using custom npm script and prefix arg

this accepts a prefix path which should be platform-agnostic.

action.yml

@@ -21,7 +21,7 @@ runs:
   using: 'composite'
   steps:
     - name: Publish Action Package
-      run: 'node ${{github.action_path}}/dist/index.js'
+      run: 'npm --prefix ${{github.action_path}} start'
       shell: bash
       id: publish
       env:

package.json

@@ -33,6 +33,7 @@
     "package": "ncc build src/index.ts --license licenses.txt",
     "package:watch": "npm run package -- --watch",
     "test": "jest",
+    "start": "node dist/index.js",
     "all": "npm run format:write && npm run lint && npm run test && npm run coverage && npm run package"
   },
   "license": "MIT",