Examine source code of JPValet

{
  "name": "JPValet",
  "version": "0.1.1",
  "manifest_version": 2,
  "icons": {
    "48": "sakura-48x48.png",
    "96": "sakura-96x96.png"
  },
  "permissions": [
    "tabs",
    "contextMenus",
    "https://learnjapanese.onl/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  }
}