Examine source code of AutoMute

{
  "manifest_version": 2,
  "name": "AutoMute",
  "description": "Automatically mutes each new tab the instant it is opened.",
  "version": "2.1.2resigned1",
  "applications": {
    "gecko": {
      "id": "AutoMute@hentschels.com"
    }
  },
  "permissions": [
    "tabs",
    "storage",
    "notifications"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": {
      "19": "Speaker_19w.png",
      "38": "Speaker_38w.png"
    },
    "default_title": "AutoMute",
    "default_popup": "browserAction.html"
  },
  "commands": {
    "mute-all": {
      "suggested_key": {
        "default": "Alt+Shift+L"
      },
      "description": "Mute all tabs"
    },
    "mute-tab": {
      "suggested_key": {
        "default": "Alt+Shift+U"
      },
      "description": "Mute current tab"
    },
    "mute-other": {
      "suggested_key": {
        "default": "Alt+Shift+O"
      },
      "description": "Mute other tabs"
    }
  },
  "icons": {
    "16": "Speaker_16.png",
    "48": "Speaker_48.png",
    "128": "Speaker_128.png"
  },
  "options_ui": {
    "page": "options.html",
    "chrome_style": true
  }
}