Examine source code of Sexy LCD clock

{
  "manifest_version": 2,
  "name": "Sexy LCD clock",
  "description": "Firefox 57+ compatible awesome LCD clock extension",
  "version": "0.2resigned1",
  "homepage_url": "https://github.com/asiniy/sexy_lcd_clock",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content_scripts/index.js"
      ],
      "css": [
        "content_scripts/index.css"
      ],
      "all_frames": false
    }
  ],
  "background": {
    "scripts": [
      "background/index.js"
    ]
  },
  "web_accessible_resources": [
    "assets/sound.wav"
  ],
  "permissions": [
    "activeTab",
    "tabs"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{cded2275-f525-49b3-b177-488462767032}"
    }
  }
}