add favorite action underneath image

app/assets/javascripts/posts.js

@@ -24,6 +24,7 @@
       this.initialize_post_image_resize_to_window_link();
       this.initialize_similar();
       this.initialize_replace_image_dialog();
+      this.initialize_fav_button();
 
       if ((Danbooru.meta("always-resize-images") === "true") || ((Danbooru.Cookie.get("dm") != "1") && (window.innerWidth <= 660))) {
         $("#image-resize-to-window-link").click();
@@ -248,6 +249,9 @@
     }
   }
 
+  Danbooru.Post.initialize_fav_button = function() {
+  }
+
   Danbooru.Post.initialize_favlist = function() {
     $("#favlist").hide();
     $("#hide-favlist-link").hide();