fix reorder

lib/Timeline.js

@@ -158,7 +158,7 @@ let Timeline = class Timeline extends lit_element_1.LitElement {
                         this.rows.splice(idx + r.parent.children.indexOf(r) + 1, 0, r);
                     }
                     else {
-                        this.rows.splice(idx + r.parent.children.length + 1, 0, r);
+                        this.rows.splice(idx + r.parent.children.length, 0, r);
                         r.parent.children = [...r.parent.children, r];
                     }
                 }

src/Timeline.ts

@@ -210,7 +210,7 @@ class Timeline extends LitElement {
           if (alreadyChild) {
             this.rows.splice(idx + r.parent.children.indexOf(r) + 1, 0, r);
           } else {
-            this.rows.splice(idx + r.parent.children.length + 1, 0, r);
+            this.rows.splice(idx + r.parent.children.length, 0, r);
             r.parent.children = [...r.parent.children, r];
           }
         }