Examine source code of Subtract

{
  "manifest_version": 2,
  "name": "Subtract",
  "description": "A minimalist productivity extension. Block distractions, set daily goals, and focus.",
  "version": "1.2.0",
  "icons": {
    "16": "icons/16.png",
    "32": "icons/32.png",
    "48": "icons/48.png",
    "128": "icons/128.png"
  },
  "permissions": [
    "storage",
    "webNavigation",
    "tabs",
    "alarms",
    "notifications",
    "<all_urls>"
  ],
  "optional_permissions": [
    "history",
    "bookmarks",
    "downloads"
  ],
  "web_accessible_resources": [
    "fonts/*.woff2",
    "content-scripts/content.css"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "hello@subtract.life"
    }
  },
  "commands": {
    "toggleMainDialog": {
      "suggested_key": {
        "default": "Alt+J"
      },
      "description": "Toggle the Subtract command palette."
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "chrome_url_overrides": {
    "newtab": "newtab.html"
  },
  "browser_action": {
    "default_title": "subtract",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content-scripts/content.js"
      ]
    }
  ]
}