Examine source code of EmojiTyper

{
  "description": "Adds the ability to type out emojis using real words",
  "manifest_version": 2,
  "name": "EmojiTyper",
  "version": "1.0",
  "homepage_url": "https://github.com/b-w-wilson/emojityper",
  "permissions": [],
  "icons": {
    "128": "icons/emojityper.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "emojityper.js"
      ]
    }
  ]
}