Add alternative way to add image alt text

entry.go

@@ -240,6 +240,11 @@ func computeExtraSettings(entry *Entry) error {
 			for _, image := range strings.Split(strings.TrimPrefix(text, "images: "), ",") {
 				entry.images = append(entry.images, Image{url: image})
 			}
+		} else if strings.HasPrefix(text, "image-alts: ") {
+			// Image alt
+			for i, alt := range strings.Split(strings.TrimPrefix(text, "image-alts: "), ",") {
+				entry.images[i].alt = alt
+			}
 		} else if strings.HasPrefix(text, "audio: ") {
 			// Audio
 			entry.audio = strings.TrimPrefix(text, "audio: ")