[6.6] Emit storefront build files into new directory

[shyim]

With 6.6 the dist folder changed. We need to write the files into a separate folder. We may want to write into both directories 🤔, to be compatible between 6.5 and 6.6

[shyim]

https://github.com/FriendsOfShopware/shopware-cli/commit/41ab58b069e1a353105a6512d533684c304017a9