Added fs-extra as a direct dependency of Blendid

[maoueh]

The fs-extra is required directly by Blendid in file gulpfile.js/tasks/replace-files.js. However, this dependency was expected to be present transitively via browser-sync.

Since it's a direct dependency of Blendid, it should be listed as such in the package.json. By not being present, it was causing us problem when using Yarn workspaces where fs-extra was not resolvable correctly (because it was in different node_modules folder).

Used version [email protected] to remain the same as browser-sync#fs-extra.