enable content negotiation (e.g return Webp image if client supports webp)

[vincentsarago]

in

titiler/src/titiler/core/titiler/core/factory.py

Lines 520 to 521 in d4741eb

	if not format:
	format = ImageType.jpeg if data.mask.all() else ImageType.png

we return either a PNG or a JPEG based on the mask, but we could also return a Webp based on the request accept header value (see https://github.com/developmentseed/tifeatures/blob/6def23bc57b547fda06b718f493d4d20ec369a35/tifeatures/dependencies.py#L102-L114)