Examine source code of Sim Tab

{
  "manifest_version": 2,
  "name": "Sim Tab",
  "short_name": "sim-tab",
  "description": "My simple new tab override extension",
  "version": "1.0.3",
  "browser_specific_settings": {
    "gecko": {
      "strict_min_version": "55.0",
      "id": "{a0535c30-c62a-434d-ac9c-3f4ef436896b}"
    }
  },
  "chrome_settings_overrides": {
    "homepage": "./src/index.html"
  },
  "chrome_url_overrides": {
    "newtab": "./src/index.html"
  },
  "background": {
    "persistent": false,
    "page": "background.html"
  },
  "permissions": [
    "storage",
    "topSites"
  ]
}