Examine source code of Lemur

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#27381c",
      "tab_background_text": "#f3ffe0"
    }
  },
  "version": "2.0",
  "name": "Lemur",
  "manifest_version": 2,
  "description": "Stock credit: <a rel=\"nofollow\" href=\"https://outgoing.prod.mozaws.net/v1/56a1e1bec2aa95523772d762430d9935f0e9eb999cd05564c1c1c4b78314434e/https%3A//pixabay.com/en/users/MarkThomas-3675305/\">Mark Thomas \n</a>"
}