Examine source code of Example Domain Blocker

{
  "manifest_version": 2,
  "name": "Example Domain Blocker",
  "version": "1.0",
  "description": "Blocks access to specified websites",
  "permissions": [
    "declarativeNetRequest",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "web_accessible_resources": [
    "block_websites.json"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{20a95105-ab0c-46b4-88d3-f9ea413032a8}"
    }
  }
}