Examine source code of NoToMailto

{
  "manifest_version": 2,
  "name": "NoToMailto",
  "description": "Say no to mailto",
  "version": "1.0.1",
  "icons": {
    "64": "icons/icon_64.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "notomailto@webext"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content_script.js"
      ]
    }
  ],
  "permissions": [
    "storage"
  ],
  "options_ui": {
    "page": "options/index.html"
  }
}