Use local path within the root directory

Otherwise, npm will not hoist the `scripts` dependencies in the
node_modules root directory, but within node_modules/@wordpress/scripts/node_modules
which won't work.

This means the @wordpress/scripts package (and other deps) need
to be copied here for testing purposes. See
WordPress/gutenberg#12437 (comment)

package.json

@@ -18,6 +18,6 @@
   },
   "homepage": "https://github.com/nosolosw/blocksettingsmenu-plugin#readme",
   "devDependencies": {
-    "@wordpress/scripts": "file:../gutenberg/packages/scripts"
+    "@wordpress/scripts": "file:./scripts"
   }
 }