Emojis to Emoji

manifest.json

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "manifest_version": 2,
  "name": "Emojis to Emoji",
  "version": "1.2",
  "description": "Replaces the text 'emojis' with 'emoji'.",
  "content_scripts": [
    {
      "matches": [
        "*://*/*"
      ],
      "js": [
        "content_script.js"
      ],
      "run_at": "document_end"
    }
  ],
  "icons": {
    "128": "icon.png"
  }
}