I'm trying to create an alarm using `browser.alarms` API for web extensions.
To make the extension cross-browser, I am using webextension-polyfill and testing on Chrome.

My code to create an alarm within a background script is shown below:

```
browser.alarms.create('spline-items-notification', {
  periodInMinutes: 1
});

```

However, when I attempt to run this extension, I always get an error:

```
Uncaught TypeError: Cannot read property 'create' of undefined

```

I am loading webextension-polyfill before the background script in manifest.json, and other interfaces work, like `browser.notifications`.

I would like to know how to fix this if possible. Thank you.