Examine source code of ezpp!

{
  "manifest_version": 2,
  "name": "ezpp!",
  "description": "Calculate pp for a beatmap directly in your browser.",
  "version": "1.10.2",
  "icons": {
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "applications": {
    "gecko": {
      "id": "ezpp@bittipiilo.com"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "*://osu.ppy.sh/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "page_action": {
    "default_icon": "icon48.png",
    "default_popup": "popup.html"
  },
  "permissions": [
    "tabs",
    "storage",
    "https://*.ppy.sh/",
    "http://*.ppy.sh/"
  ]
}