alt-attribute for mail replacement image missing

Google PageSpeed critizises the missing alt-attribute for the replacement images. Please maybe add an option in the Image Settings.

For those who can’t wait for an official option, this snippet adds the alt-attribute “E-Mail” (and in my case, also adds >15 PageSpeed points):

add_filter('eeb/validate/get_protected_display', 'cy_email_encoder_img_alt');
function cy_email_encoder_img_alt($content) {
	return preg_replace('/(\<img[^>]+\?eeb_mail\=[^>]+)/', '$1 alt="E-Mail"', $content);
}