Provide invokables for common drop query keys (#8165)

Merge pull request 8165

lib/jekyll/drops/document_drop.rb

@@ -64,6 +64,18 @@ module Jekyll
           result[key] = doc[key] unless NESTED_OBJECT_FIELD_BLACKLIST.include?(key)
         end
       end
+
+      def title
+        @obj.data["title"]
+      end
+
+      def categories
+        @obj.data["categories"]
+      end
+
+      def tags
+        @obj.data["tags"]
+      end
     end
   end
 end

lib/jekyll/drops/page_drop.rb

@@ -9,6 +9,10 @@ module Jekyll
 
       def_delegators :@obj, :content, :dir, :name, :path, :url
       private def_delegator :@obj, :data, :fallback_data
+
+      def title
+        @obj.data["title"]
+      end
     end
   end
 end