fix link to Extensions Guide docs
fix link to Extensions Guide docs

bhanu22776/spree_fancy_theme,mvjohn100/spree_fancy,spree-contrib/spree_fancy,samuels410/spree_fancy,kewaunited/spree_fancy,kewaunited/spree_fancy,mvjohn100/spree_fancy,rsempe/spree_fancy,rsempe/spree_fancy,samuels410/spree_fancy,rsempe/spree_fancy,quentinuys/spree_fancy,spree-contrib/spree_fancy,quentinuys/spree_fancy,bhanu22776/spree_fancy_theme,spree-contrib/spree_fancy,kewaunited/spree_fancy,quentinuys/spree_fancy