[feature] Refetch emojis when they change on remote instances (#905)

* select emoji using image_static_url

* use updated on AP emojis

* allow refetch of updated emojis

* cheeky workaround for test

* clean up old files for refreshed emoji

* check error for originalPostData

* shorten GetEmojiByStaticImageURL

* delete kirby (sorry nintendo)

internal/ap/extract.go

@@ -535,6 +535,11 @@ func ExtractEmoji(i Emojiable) (*gtsmodel.Emoji, error) {
 	emoji.Disabled = new(bool)
 	emoji.VisibleInPicker = new(bool)
 
+	updatedProp := i.GetActivityStreamsUpdated()
+	if updatedProp != nil && updatedProp.IsXMLSchemaDateTime() {
+		emoji.UpdatedAt = updatedProp.Get()
+	}
+
 	return emoji, nil
 }