Examine source code of Pinboard Button

{
  "name": "Pinboard Button",
  "description": "A minimal Firefox extension for Pinboard (https://pinboard.in) that doesn't use API keys, but just opens Pinboard windows.",
  "homepage_url": "https://github.com/fiatjaf/firefox-pinboard-popup/",
  "manifest_version": 2,
  "version": "0.6",
  "applications": {
    "gecko": {
      "id": "{eb059682-fdfe-4250-a2c2-7f7d1af4fe85}"
    }
  },
  "permissions": [
    "activeTab",
    "contextMenus"
  ],
  "web_accessible_resources": [
    "close.html"
  ],
  "background": {
    "scripts": [
      "pinboard.js",
      "background.js"
    ]
  },
  "commands": {
    "save-to-pinboard": {
      "suggested_key": {
        "default": "Alt+P"
      },
      "description": "Save current page to Pinboard"
    },
    "save-to-read-later": {
      "suggested_key": {
        "default": "Alt+R"
      },
      "description": "Save current page to Pinboard's \"to read\" list"
    }
  },
  "browser_action": {
    "browser_style": true,
    "default_title": "Pinboard",
    "default_popup": "popup.html",
    "default_icon": "icon-dark.svg",
    "theme_icons": [
      {
        "light": "icon-light.svg",
        "dark": "icon-dark.svg",
        "size": 32
      }
    ]
  },
  "icons": {
    "48": "icon-addon.png",
    "128": "icon-addon.png"
  }
}