ion icons not displayed if they are hosted on a server requesting auth

I'm submitting a:

[x] bug report
[ ] feature request
[ ] support request

**ionicons version:**
```
ionicons v4.4.6
```

Current behavior:
Currently the icon class gets the svg content without sending the cookies in microsoft edge on desktop and in every navigator on iPad. By default, fetch won't send or receive any cookies from the server, resulting in unauthenticated requests if the site relies on maintaining a user session (to send cookies, the credentials init option must be set). This means that those svgs can't be hosted on a server requesting auth.

Expected behavior:
I would expect that a credentials init option is set to same-origin or include.

If there are cases I haven't thought of, please let me know. I'd also be happy with a config option to change the value.

首先定位获取 SVG 内容的图标类实现，并检查其 fetch 选项的设置方式。在 Edge 或 iPad 上使用托管在身份验证之后的图标重现该问题，然后验证请求是否保留了所需的会话凭据，以及现有的未经过身份验证的图标加载是否仍然正常工作。

由索引模型根据 Issue 内容生成。