Examine source code of Reading Helper

{
  "manifest_version": 2,
  "name": "Reading Helper",
  "version": "1.1",
  "description": "Adds a semi-transparent bar to the screen that follows your mouse. Helps with focusing on one line at a time.",
  "permissions": [
    "storage"
  ],
  "browser_action": {
    "default_popup": "popup/settings.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "main.js"
      ],
      "all_frames": true
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "type": "module"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{8b37bf57-8855-47f1-8d5a-962a94216c5f}"
    }
  }
}