Uploads a file to a signed URL created with CreateUploadSignedUrl().
buckets permissions: noneobjects permissions: insertvar imagePath = Path.Combine("Assets", "fancy-avatar.png");
var signedUrl = await supabase.Storage.From("avatars").CreateUploadSignedUrl("fancy-avatar.png");
await supabase.Storage.From("avatars").UploadToSignedUrl(imagePath, signedUrl);