Examine source code of Character Counter Tool

{
  "manifest_version": 2,
  "name": "Character Counter Tool",
  "version": "1.0",
  "description": "Counts the number of characters and words in your text.",
  "permissions": [
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "Character Counter",
    "default_icon": {
      "48": "icon.png"
    },
    "default_popup": "popup.html"
  },
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{640e2746-642f-4586-90d8-dbd5364805bf}"
    }
  }
}