GUI: update tig installation targets

Author: dotnetCarpenter

data/guis/tig.yml

@@ -3,6 +3,8 @@ name: "tig"
 project_url: "https://github.com/jonas/tig#readme"
 image_tag: "images/guis/[email protected]"
 platforms:
+  - "Windows"
+  - "Mac"
   - "Linux"
 price: "Free"
 license: "GPL-2.0"