Examine source code of Simplify Gmail

{
  "name": "Simplify Gmail",
  "version": "3.4.2",
  "description": "Make Gmail simpler, more capable, and more respectful",
  "homepage_url": "https://simpl.fyi",
  "default_locale": "en",
  "manifest_version": 3,
  "icons": {
    "48": "img/app/icon48.png",
    "128": "img/app/icon128.png",
    "512": "img/app/icon512.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://mail.google.com/*"
      ],
      "css": [
        "css/images.css",
        "css/simplifyGmail.css"
      ],
      "js": [
        "js/simplifyGmail.js"
      ],
      "run_at": "document_start",
      "all_frames": false
    }
  ],
  "action": {
    "default_icon": {
      "48": "img/app/icon48.png",
      "128": "img/app/icon128.png"
    },
    "default_title": "Simplify for Gmail",
    "default_popup": "misc/popup.html"
  },
  "declarative_net_request": {
    "rule_resources": [
      {
        "id": "simplifyTrackerList",
        "enabled": true,
        "path": "misc/trackers.json"
      }
    ]
  },
  "background": {
    "scripts": [
      "js/background.js"
    ]
  },
  "options_ui": {
    "page": "misc/permissions.html",
    "open_in_tab": true
  },
  "web_accessible_resources": [
    {
      "resources": [
        "misc/*",
        "img/**",
        "fonts/*",
        "js/authUser.js"
      ],
      "matches": [
        "https://mail.google.com/*"
      ]
    }
  ],
  "permissions": [
    "storage",
    "declarativeNetRequestWithHostAccess"
  ],
  "optional_permissions": [
    "downloads"
  ],
  "host_permissions": [
    "https://mail.google.com/*",
    "https://*.googleusercontent.com/*"
  ],
  "content_security_policy": {
    "extension_pages": "default-src 'self'; style-src 'self'; script-src 'self'; img-src 'self'"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{a4c1064c-95dd-47a7-9b02-bb30213b7b29}",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}