Examine source code of On this Day

{
  "manifest_version": 2,
  "name": "On this Day",
  "version": "1.0.1",
  "description": "Events that happened on the same day, different year, in history!",
  "author": "@dootdoot1111",
  "icons": {
    "32": "images/icon.png"
  },
  "browser_action": {
    "default_icon": {
      "32": "images/icon.png"
    },
    "default_title": "OTD",
    "default_popup": "popup.html"
  }
}