Examine source code of Promute

{
  "name": "Promute",
  "manifest_version": 2,
  "version": "1.0.10",
  "description": "Promute automatically mutes twitter accounts sending promotions to your timeline as you scroll by.",
  "icons": {
    "16": "./logo_16.png",
    "48": "./logo_48.png",
    "128": "./logo_128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://twitter.com/*"
      ],
      "js": [
        "promute.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{a617e176-3b81-47db-be52-a2ab8428a532}"
    }
  }
}