Examine source code of Twilter

{
  "manifest_version": 2,
  "name": "Twilter",
  "version": "1.1resigned1",
  "description": "Filter tweets from a specified user/with a specified string to an user defined text",
  "homepage_url": "https://github.com/yanorestes/twilter-firefox",
  "icons": {
    "48": "icons/filter.svg",
    "96": "icons/filter.svg"
  },
  "permissions": [
    "activeTab",
    "storage"
  ],
  "browser_action": {
    "default_icon": "icons/filter.svg",
    "default_title": "Twilter",
    "default_popup": "popup/filter_settings.html"
  },
  "content_scripts": [
    {
      "matches": [
        "*://twitter.com/*"
      ],
      "js": [
        "jquery-3.3.1.min.js",
        "twilter.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{a9278967-691d-496f-bf3c-ca89c166de24}"
    }
  }
}