Examine source code of lpst

{
  "manifest_version": 2,
  "name": "lpst",
  "version": "1.2.2",
  "description": "Lichess Puzzle Streak Timer",
  "icons": {
    "48": "icons/lpst.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.lichess.org/*"
      ],
      "js": [
        "lpst.js"
      ],
      "css": [
        "lpst.css"
      ]
    }
  ],
  "browser_action": {
    "browser_style": true,
    "default_icon": {
      "48": "icons/lpst.png"
    },
    "default_title": "Lichess Puzzle Streak Timer",
    "default_popup": "popup/popup.html"
  },
  "options_ui": {
    "browser_style": true,
    "open_in_tab": true,
    "page": "options/options.html"
  },
  "permissions": [
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{6da928b3-9be8-4564-959d-2923633cc035}"
    }
  }
}