Switch www. deployment to Alkane

Summary:
Previously, www. was deployed through staging repository.

This change sets instead Alkane recipes to deploy the site.

Ref T2014

Reviewers: aceppaluni, DorianWinty

Reviewed By: DorianWinty

Maniphest Tasks: T2014

Differential Revision: https://devcentral.nasqueron.org/D3438