Fix: Theme images are broken on the VS Code welcome page
## Problem
The theme images on the welcome screen are not showing.

The browser is complaining about the domain of the image being different:
```
Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at https://xn--workspacefe5a5e0fff874414-web-ide-server-uq60i.remotedev.10.0.0.216.nip.io/oss-45929ecac2e431d04eeb3e17295e456625625845/static/out/vs/workbench/contrib/welcomeGettingStarted/common/media/dark.png. (Reason: CORS request did not succeed). Status code: (null).
```
(notice the `xn--` unicode indicator in the domain)
However, then the browser says that the correct URL returns 404 `https://workspacefe5a5e0fff874414-web-ide-server-8000.remotedev.10.0.0.216.nip.io/oss-45929ecac2e431d04eeb3e17295e456625625845/static/out/vs/workbench/contrib/welcomeGettingStarted/common/media/dark.png` But this URL works directly.

epic