Make sure to actually use yarn to install the main-packages, otherwise the packages.json#resolutions property will not be used and @babel/helpers would not get overruled

Overruled @babel/helpers to fix how initializers play with decorated properties. Thus circumventing the imperformant and lengthy code being generated by babel in the non-legacy option.

test/.babelrc

@@ -7,7 +7,7 @@
     }]
   ],
   "plugins": [
-    [ "@babel/plugin-proposal-decorators", { "decoratorsBeforeExport": true }],
+    [ "@babel/plugin-proposal-decorators", { "legacy": true }],
     [ "@babel/plugin-proposal-class-properties", { "loose":  true } ],
     [ "@babel/plugin-proposal-private-methods", {"loose":  true } ],
     [ "@babel/plugin-proposal-optional-chaining" ],

test/todos-mvc/components/my-todo.jsx

@@ -7,20 +7,10 @@ import {TodoItem} from './todo-item';
 @defineElement('my-todo')
 export class MyTodo extends CustomElement{
     uid = 1;
-    @State() todos;
-    // = [
-    //     {id: this.uid++, text: "my initial todo", checked: false },
-    //     {id: this.uid++, text: "Learn about Web Components", checked: false },
-    // ];
-    
-    constructor(){
-        super();
-        this.uid = 1;
-        this.todos = [
-            {id: this.uid++, text: "my initial todo", checked: false },
-            {id: this.uid++, text: "Learn about Web Components", checked: false },
-        ]
-    }
+    @State() todos = [
+        {id: this.uid++, text: "my initial todo", checked: false },
+        {id: this.uid++, text: "Learn about Web Components", checked: false },
+    ];
     
     render(){
         return (