Examine source code of AO3rdr

{
  "manifest_version": 2,
  "name": "ao3rdr",
  "version": "1.8.2resigned1",
  "permissions": [
    "activeTab",
    "storage",
    "tabs",
    "https://boiling-caverns-2782.herokuapp.com/*",
    "https://*.ao3rdr.com/*"
  ],
  "description": "Rating system and block by tag system for Archive of Our Own.",
  "icons": {
    "16": "data/images/icon_16.png",
    "48": "data/images/icon_48.png",
    "128": "data/images/icon_128.png"
  },
  "applications": {
    "gecko": {
      "id": "jid1-ayTtY9e4Iz49HA@jetpack",
      "strict_min_version": "57.0"
    }
  },
  "background": {
    "scripts": [
      "src/background-chrome.js",
      "src/background.js",
      "src/article.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "*://archiveofourown.org/*",
        "https://*.ao3rdr.com/*"
      ],
      "js": [
        "lib/jquery-3.3.1.min.js",
        "src/ao3lib.js",
        "src/toolbar-ao3.js",
        "src/toolbar-chrome.js",
        "src/toolbar-content.js",
        "src/article.js",
        "data/settings/articles-table-chrome.js",
        "src/images.js",
        "src/contentscript.js"
      ],
      "css": [
        "data/style.css"
      ],
      "all_frames": true,
      "run_at": "document_start"
    }
  ],
  "browser_action": {
    "default_title": "AO3rdr",
    "default_popup": "data/settings/popup.html",
    "default_icon": "data/images/icon_128.png",
    "browser_style": true
  },
  "web_accessible_resources": [
    "data/settings/articles-table-chrome.js",
    "data/settings/articles-table-content.js",
    "data/settings/articles-table.js",
    "data/settings/articles-table-lib.js",
    "data/settings/credits.html",
    "data/settings/index.html",
    "data/settings/jquery.tagsinput.css",
    "data/settings/jquery.tagsinput.js",
    "data/settings/popup.html",
    "data/settings/popup.js",
    "data/settings/css/custom.css",
    "data/settings/css/normalize.css",
    "data/settings/css/skeleton.css",
    "data/images/bookmark-fill.svg",
    "data/images/bookmark.svg",
    "data/images/close.svg",
    "data/images/cloud-offline.svg",
    "data/images/cloud-ok.svg",
    "data/images/cloud-sync.svg",
    "data/images/dislike-fill.svg",
    "data/images/dislike.svg",
    "data/images/flag.svg",
    "data/images/hidden.svg",
    "data/images/icon_128.png",
    "data/images/icon_16.png",
    "data/images/icon_48.png",
    "data/images/icon.png",
    "data/images/icon.svg",
    "data/images/menu.svg",
    "data/images/read.svg",
    "data/images/star-0.svg",
    "data/images/star-1-fill.svg",
    "data/images/star-1.svg",
    "data/images/star-3-fill.svg",
    "data/images/star-3.svg",
    "data/images/star-5-fill.svg",
    "data/images/star-5.svg",
    "data/images/sync.svg",
    "data/images/unread.svg"
  ]
}