Examine source code of Inject2Download

{
  "manifest_version": 2,
  "name": "Inject2Download",
  "description": "video url grabber",
  "version": "1.0",
  "icons": {
    "64": "icons/icon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.mozilla.org/*"
      ],
      "js": [
        "content_script.js"
      ]
    }
  ],
  "browser_action": {
    "default_icon": {
      "64": "icons/icon.png"
    },
    "default_popup": "browserAction/index.html",
    "default_title": "Inject2Download"
  },
  "web_accessible_resources": [
    "public/**/*.png",
    "public/**/*",
    "public/*",
    "*",
    "public/**/*.jpg",
    "public/*.woff2"
  ],
  "page_action": {
    "default_icon": {
      "64": "icons/icon.png"
    },
    "default_popup": "content_script.js",
    "default_title": "Inject2Download"
  }
}