Examine source code of A-B Loop

{
  "manifest_version": 2,
  "name": "A-B Loop",
  "description": "Loop between points in a video.",
  "version": "3",
  "icons": {
    "48": "./icons/icon48.png",
    "96": "./icons/icon96.png"
  },
  "applications": {
    "gecko": {
      "id": "abloop@abloop.com",
      "strict_min_version": "59.0"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://*/*"
      ],
      "css": [],
      "js": [
        "browser-polyfill.min.js",
        "messages.js",
        "ABLooper.js",
        "content-script.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "page_action": {
    "show_matches": [
      "*://*/*"
    ],
    "browser_style": true,
    "default_icon": {
      "19": "./icons/icon19.png",
      "38": "./icons/icon38.png"
    },
    "default_popup": "./popup/index.html",
    "default_title": "A-B Loop"
  },
  "options_ui": {
    "browser_style": false,
    "open_in_tab": true,
    "page": "./options/index.html"
  },
  "permissions": [
    "*://*/*"
  ]
}