Gmail character counter

manifest.json

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "name": "Gmail character counter",
  "description": "Write 280 characters emails in Gmail",
  "version": "0.1",
  "content_scripts": [
    {
      "matches": [
        "https://mail.google.com/*",
        "https://inbox.google.com/*"
      ],
      "js": [
        "inboxsdk.js",
        "content.js",
        "js/jquery.js",
        "js/compromise.min.js"
      ],
      "css": [
        "styles.css"
      ],
      "run_at": "document_start"
    }
  ],
  "browser_action": {
    "default_icon": "short.png"
  },
  "icons": {
    "16": "icon16.png",
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "web_accessible_resources": [
    "short.png",
    "icon16.png"
  ],
  "permissions": [
    "https://mail.google.com/",
    "https://inbox.google.com/"
  ],
  "manifest_version": 2
}