Examine source code of Manual Code Injector

{
  "manifest_version": 2,
  "name": "Manual Code Injector",
  "version": "1.2.1",
  "description": "Inject personal code using customizable hotkeys",
  "permissions": [
    "<all_urls>",
    "activeTab",
    "storage",
    "tabs",
    "unlimitedStorage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "@manualcodeinjector"
    }
  },
  "icons": {
    "16": "./icons/icon-16.png",
    "32": "./icons/icon-32.png",
    "48": "./icons/icon-48.png",
    "128": "./icons/icon-128.png"
  },
  "browser_action": {
    "browser_style": true,
    "default_icon": "./icons/icon-32.png",
    "default_popup": "./popup/index.html",
    "default_title": "ManualCodeInjector"
  },
  "options_ui": {
    "browser_style": true,
    "open_in_tab": true,
    "page": "./index.html"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "main.js"
      ]
    }
  ]
}