Examine source code of Crewlist for Firefox

{
  "manifest_version": 2,
  "default_locale": "en",
  "name": "Crewlist for Firefox",
  "description": "Upgrade your email experience with Crewlist for Firefox",
  "version": "1.1.16",
  "applications": {
    "gecko": {
      "id": "crewlistforfirefox@crewlist.co.nz"
    }
  },
  "author": "Crewlist Ltd",
  "browser_action": {
    "default_popup": "src/index.html",
    "default_title": "Crewlist for Firefox"
  },
  "icons": {
    "16": "src/icon16.png",
    "32": "src/icon32.png",
    "48": "src/icon48.png",
    "128": "src/icon128.png"
  },
  "permissions": [
    "storage",
    "*://api.crewlist.co/*",
    "*://crewlist.co.nz/*",
    "*://crewlist.s3.amazonaws.com/*"
  ],
  "background": {
    "scripts": [
      "dist/background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "*://mail.google.com/*"
      ],
      "css": [
        "src/stylesheet.gmail-cl-1.2.241.css"
      ],
      "js": [
        "dist/gmailJsLoader.js",
        "dist/extension.js",
        "src/jquery-3.5.1.min.js",
        "src/sha512.js",
        "src/jquery.ba-throttle-debounce.min.js"
      ],
      "run_at": "document_start"
    }
  ],
  "web_accessible_resources": [
    "dist/gmailJsLoader.js",
    "dist/extension.js",
    "src/jquery-3.5.1.min.js",
    "src/jquery.ba-throttle-debounce.min.js",
    "src/sha512.js",
    "src/index.html",
    "src/stylesheet.firefox-cl-1.2.241",
    "src/stylesheet.gmail-cl-1.2.241",
    "src/stylesheet.theme-cl-1.2.241"
  ]
}