Images with CORS fail in custom server mode

[corbindavenport]

If an image is on a server with a CORS same origin policy (example), it doesn't work in custom server mode, because Alt Text Generator can't fetch it again to convert to base64:

Recieved page from context menu: 
Object { menuItemId: "generate-alt", parentMenuItemId: 855, viewType: "tab", mediaType: "image", frameId: 0, editable: false, srcUrl: "https://hfu.hollywoodfeed.com/wp-content/uploads/2024/03/GettyImages-496236528-scaled.jpg", pageUrl: "https://hfu.hollywoodfeed.com/wp-content/uploads/2024/03/GettyImages-496236528-scaled.jpg", modifiers: [], button: 0 }
[background.js:220:11](moz-extension://3b9ede34-aea6-4eb7-b105-ac8d18a826bb/js/background.js)
Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at https://hfu.hollywoodfeed.com/wp-content/uploads/2024/03/GettyImages-496236528-scaled.jpg. (Reason: CORS header ‘Access-Control-Allow-Origin’ missing). Status code: 200.

Ideally this should be fixed, if not then a better error message would be helpful instead of just failing silently or showing messages in the LM Studio logs.