Examine source code of Fatebook for Firefox

{
  "name": "Fatebook for Firefox",
  "description": "The fastest way to make and track predictions",
  "homepage_url": "https://fatebook.io/",
  "version": "1.0.6",
  "manifest_version": 3,
  "action": {
    "default_title": "Click to make a prediction",
    "default_icon": {
      "16": "scale16.png",
      "32": "scale32.png",
      "48": "scale48.png",
      "128": "scale128.png"
    }
  },
  "icons": {
    "16": "scale16.png",
    "32": "scale32.png",
    "48": "scale48.png",
    "128": "scale128.png"
  },
  "author": "hello@sage-future.org",
  "short_name": "Fatebook",
  "commands": {
    "open_modal": {
      "suggested_key": {
        "default": "Ctrl+Alt+Q",
        "mac": "Command+Alt+Q"
      },
      "description": "Make a new prediction, from any webpage."
    }
  },
  "web_accessible_resources": [
    {
      "matches": [
        "https://*/*",
        "http://*/*"
      ],
      "resources": [
        "/direct_inject*",
        "*.png"
      ]
    }
  ],
  "content_scripts": [
    {
      "run_at": "document_idle",
      "js": [
        "after.js"
      ],
      "css": [
        "style.css"
      ],
      "matches": [
        "https://*/*",
        "http://*/*"
      ]
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "tabs",
    "scripting"
  ],
  "host_permissions": [
    "https://*/*",
    "http://*/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "extension@fatebook.io"
    }
  },
  "optional_permissions": [
    "https://*/*",
    "http://*/*"
  ]
}