Examine source code of ProToots

{
  "manifest_version": 2,
  "name": "ProToots",
  "version": "1.2.3",
  "icons": {
    "48": "icons/icon small_size/icon small_size.png",
    "96": "icons/icon small_size/icon small_size.png"
  },
  "description": "puts pronouns next to usernames on mastodon",
  "homepage_url": "https://github.com/ItsVipra/ProToots",
  "permissions": [
    "storage",
    "https://en.pronouns.page/api/*"
  ],
  "browser_action": {
    "default_icon": "icons/icon small_size/icon small_size.png",
    "default_title": "ProToots",
    "default_popup": "options/options.html"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*/*"
      ],
      "js": [
        "content_scripts/protoots.js"
      ],
      "css": [
        "styles/proplate.css"
      ],
      "run_at": "document_start"
    }
  ],
  "options_ui": {
    "page": "options/options.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "protoots@trans.rights"
    }
  }
}