Examine source code of ReadCast

{
  "name": "ReadCast",
  "version": "1.1",
  "manifest_version": 2,
  "description": "Save articles to your ReadCast library straight from your browser.",
  "homepage_url": "https://readcast.app",
  "browser_action": {
    "default_icon": {
      "19": "./icons/favicon-16x16.png",
      "38": "./icons/favicon-16x16.png"
    },
    "default_title": "ReadCast"
  },
  "icons": {
    "16": "./icons/favicon-16x16.png",
    "128": "./icons/favicon-150x150.png"
  },
  "permissions": [
    "activeTab",
    "tabs"
  ],
  "background": {
    "persistent": false,
    "scripts": [
      "./js/background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "http://*/*",
        "https://*/*"
      ],
      "js": [
        "./js/injectMessage.js"
      ]
    }
  ]
}