feat: use fork of scratch-storage

This fork overrides the `output.publicPath` option to fix asset URLs.

See https://github.com/RaspberryPiFoundation/scratch-storage for more detail.s

Author: sebjacobs

.npmrc

@@ -0,0 +1,5 @@
+@raspberrypifoundation:registry=https://npm.pkg.github.com
+//npm.pkg.github.com/:_authToken=${NPM_AUTH_TOKEN}
+strict-peer-deps=true
+engine-strict=true
+loglevel=error