Hovercard SDK docs don't mention Gravatar.init()

# Bug Report

## Description / Observed Behavior

I followed the instructions at https://docs.gravatar.com/sdk/hovercards/, but it did not result in a working Hovercard.

## Expected Behavior

I expected my Gravatar image to have a card show up when I hovered over it.

## Repro Steps / Code Example

Share the steps to reproduce the issue, screenshots, or a [CodeSandbox](https://codesandbox.io) link is also appreciated!

## Your Environment

- Component/Service Name and Version: davidtucker.name
- Platform: Web
- Operating System / Browser: Firefox on Pop OS!

## Additional Information

I had to add this to the `` to get it to work:
```javascript

window.addEventListener("DOMContentLoaded", function () {
if (window.Gravatar) {
window.Gravatar.init();
}
});

```

Start with the Hovercard SDK documentation at https://docs.gravatar.com/sdk/hovercards/ and review the initialization steps, including the provided Gravatar.init() example. Done means the instructions explain the required initialization so following them produces a working hovercard.

Written by the indexing model from the issue text.