dataUriMatcher function
Implementation
ImageSourceMatcher dataUriMatcher({String? encoding = 'base64', String? mime}) => (attributes, element) {
if (_src(attributes) == null) return false;
final dataUri = _dataUriFormat.firstMatch(_src(attributes)!);
return dataUri != null &&
(mime == null || dataUri.namedGroup('mime') == mime) &&
(encoding == null || dataUri.namedGroup('encoding') == ';$encoding');
};