Fix media type with optional parameters (#7739)

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I am having an issue loading this image
"https://stacks.stanford.edu/image/iiif/wy534zh7137/SULAIR_rosette/full/400,/0/default.jpg".
It has a mime type of "image/jpeg; charset=utf-8", which is not common.

The code doesn't parse the full string that includes the optional
parameter "charset=utf-8" to create the jpeg image format.

A line is added to take only the mime type in the media type before the
";" and ignore the optional parameters.

* Closes <https://github.com/emilk/egui/issues/7738>
* [x] I have followed the instructions in the PR template

Co-authored-by: leungkkf <leungkkf@gmail.com>

crates/egui_extras/src/loaders/image_loader.rs

@@ -50,8 +50,11 @@ fn is_supported_mime(mime: &str) -> bool {
         }
     }
 
+    // Some servers may return a media type with an optional parameter, e.g. "image/jpeg; charset=utf-8".
+    let (mime_type, _) = mime.split_once(';').unwrap_or((mime, ""));
+
     // Uses only the enabled image crate features
-    ImageFormat::from_mime_type(mime).is_some_and(|format| format.reading_enabled())
+    ImageFormat::from_mime_type(mime_type).is_some_and(|format| format.reading_enabled())
 }
 
 impl ImageLoader for ImageCrateLoader {