Examine source code of D&D Character Sync

{
  "manifest_version": 3,
  "author": "Harm Manders & Key Roos",
  "name": "D&D Character Sync",
  "description": "Store character sheets from different D&D apps",
  "version": "0.11.0",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "icons": {
    "16": "assets/icons/icon16.png",
    "32": "assets/icons/icon32.png",
    "48": "assets/icons/icon48.png",
    "128": "assets/icons/icon128.png"
  },
  "action": {
    "default_popup": "index.html",
    "default_icon": {
      "16": "assets/icons/icon16.png",
      "32": "assets/icons/icon32.png",
      "48": "assets/icons/icon48.png",
      "128": "assets/icons/icon128.png"
    }
  },
  "permissions": [
    "storage",
    "activeTab",
    "scripting",
    "tabs"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://shieldmaiden.app/*",
        "*://*.shieldmaiden.app/*",
        "*://harmlesskey.com/*",
        "*://*.harmlesskey.com/*"
      ],
      "js": [
        "content/bridge.js"
      ],
      "run_at": "document_start"
    }
  ],
  "host_permissions": [
    "*://*.dndbeyond.com/characters/*",
    "*://harmlesskey.com/content/players/*",
    "*://*.harmlesskey.com/content/players/*",
    "*://harmlesskey.com/content/characters/*",
    "*://*.harmlesskey.com/content/characters/*",
    "*://shieldmaiden.app/content/players/*",
    "*://*.shieldmaiden.app/content/players/*",
    "*://shieldmaiden.app/content/characters/*",
    "*://*.shieldmaiden.app/content/characters/*",
    "*://dicecloud.com/character/*",
    "*://v1.dicecloud.com/character/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "dnd-character-sync@harmlesskey.com",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    }
  },
  "web_accessible_resources": [
    {
      "resources": [
        "assets/fonts/*"
      ],
      "matches": [
        "<all_urls>"
      ]
    }
  ]
}