Our helpdesk was recently setup with HSTS on help.example.com. Now I can no longer use ZAT theme preview for my theme preview. I keep getting these messages for all assets served over ZAT theme preview:
```
Mixed Content: The page at '<URL>' was loaded over HTTPS, but requested an insecure element '<URL>'. This request was automatically upgraded to HTTPS, For more information see <URL>
new:1 Mixed Content: The page at 'https://mysite.zendesk.com/hc/en-us/requests/new' was loaded over HTTPS, but requested an insecure element 'http://localhost:4567/guide/settings/logo.svg'. This request was automatically upgraded to HTTPS, For more information see https://blog.chromium.org/2019/10/no-more-mixed-messages-about-https.html
```
How do I fix this?
