Examine source code of NightTimeFP theme

{
  "name": "NightTimeFP theme",
  "description": "Extension to enable multiple themes or specific styles to be applied over css on floatplane.com site.",
  "author": "Snikay",
  "version": "1.0.1",
  "permissions": [
    "activeTab",
    "storage",
    "*://*.floatplane.com/*",
    "tabs"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://*.floatplane.com/*"
      ],
      "css": [
        "assets/fp.css"
      ]
    }
  ],
  "background": {
    "scripts": [
      "common.js",
      "background.js"
    ]
  },
  "browser_action": {
    "browser_style": false,
    "default_popup": "popup.html",
    "default_title": "NightTimeFP theme",
    "default_icon": {
      "19": "images/fp19.png",
      "38": "images/fp38.png"
    }
  },
  "icons": {
    "48": "images/fp48.png",
    "96": "images/fp96.png"
  },
  "applications": {
    "gecko": {
      "id": "{b3a962bb-594a-488e-ad44-d3e3e7673c67}",
      "strict_min_version": "53.0"
    }
  },
  "manifest_version": 2
}