不能使用带有Chrome扩展功能的事件监听器

Question

我正在尝试进行chrome扩展，但是我的事件监听器不会触发。这是我的代码：

document.querySelector(".bird").ondblclick = () => init();

const init = () => {
  //hide unnessecary elements
  window.scrollTo(0, document.body.scrollHeight);
  document.querySelector("#footer").style.opacity = 0;
  document.body.style.overflow = "hidden";

  //Now we create the game UI
  let UI = document.createElement("DIV");
  UI.id = "Game-UI";

  //after we created the game UI we will append all elements to the UI
  let startText = document.createElement("SPAN");
  startText.innerHTML = "Press space to start...";
  startText.className = "startText";
  UI.append(startText);

  document.body.append(UI);

  //if the UI is loaded then we start doing things this is to prevent the script from executing to fast
  startText.addEventListener("load", flicker);
}

const flicker = () => { //this needs to fire
  console.log("this");
  (() => { //in here we do the flicker animation for the starttext
    let on = true;
    setInterval(function() {
      on != on;
      if (on) {
        console.log("reached!");
      }
    }, 2000);
  });
}

我在网上搜索，但找不到该问题的任何解决方案。我还注意到，在chrome事件检查器中找不到对注入文件的任何引用。

另外，这是我的清单：

{
  "name": "Ontdek Het Wad easteregg",
  "version": "1.0",
  "description": "Super dom dit",
  "content_scripts": [
    {
      "matches": ["https://www.ontdekhetwad.nl/*"],
      "run_at": "document_end",
      "js": ["/js/src/game.js", "/js/includes/matter.min.js"],
      "css": ["/css/gameUI.css"]
    }
  ],
  "manifest_version": 2
}