Examine source code of xTimes

{
  "manifest_version": 2,
  "name": "xTimes",
  "version": "1.3.1",
  "description": "Allows you to download cryptic crosswords from The Times in .ipuz format.",
  "icons": {
    "48": "icons/xtimes-48.png"
  },
  "permissions": [
    "tabs",
    "downloads",
    "*://*.thetimes.co.uk/puzzleclub/crosswordclub/play/crossword/*"
  ],
  "background": {
    "scripts": [
      "xtimes_bg.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "https://www.thetimes.co.uk/puzzleclub/crosswordclub/play/crossword/*"
      ],
      "all_frames": true,
      "js": [
        "xtimes_cs.js"
      ]
    }
  ],
  "page_action": {
    "default_icon": {
      "16": "icons/xtimes-16.png",
      "32": "icons/xtimes-32.png"
    },
    "show_matches": [
      "https://www.thetimes.co.uk/puzzleclub/crosswordclub/puzzles/crossword/*"
    ]
  }
}