Examine source code of LE Per Hour

{
  "manifest_version": 2,
  "name": "LE Per Hour",
  "version": "1.1",
  "description": "Browser extension for Plan vs Undead. Parse your plant's harvest time info and display a tooltip with it in a LE per hour format.",
  "homepage_url": "https://github.com/Joelmmm/LE-per-hour",
  "content_scripts": [
    {
      "matches": [
        "*://*.plantvsundead.com/*"
      ],
      "js": [
        "./src/content.js"
      ]
    }
  ],
  "permissions": [
    "tabs"
  ]
}