Add Giftoff.com to merchant

_data/merchants.yml

@@ -104,6 +104,8 @@
       url: https://cryptonic.net
     - name: Fine Art from Jeanine King ~ Artwork of Home/Archtecture, Pets, Potraits, Caricatures ~ International Shipping
       url: http://art2unlimited.webs.com/
+    - name: Digital gift cards
+      url: https://giftoff.com/
 - category: Entertainment
   merchants:
     - name: Crypto Kingdom