Add info about minimized state to comment xml.

src/engine/comment.js

@@ -26,8 +26,9 @@ class Comment {
     }
 
     toXML () {
-        return `<comment id="${this.id}" x="${this.x}" y="${
-            this.y}" w="${this.width}" h="${this.height}" pinned="${this.blockId !== null}">${this.text}</comment>`;
+        return `<comment type="scratch" id="${this.id}" x="${this.x}" y="${
+            this.y}" w="${this.width}" h="${this.height}" pinned="${
+            this.blockId !== null}" minimized="${this.minimized}">${this.text}</comment>`;
     }
 
     // TODO choose min and defaults for width and height