Add support for encrypted events in webhook replies

Obviously won't help if the encryption hardening options are enabled,
because the point of those is to prevent the bridge from decrypting old
messages.

Fixes #131

portal.go

@@ -1414,6 +1414,12 @@ func (portal *Portal) convertReplyMessageToEmbed(eventID id.EventID, url string)
 	if err != nil {
 		return nil, fmt.Errorf("failed to fetch event: %w", err)
 	}
+	if evt.Type == event.EventEncrypted {
+		evt, err = portal.bridge.Crypto.Decrypt(evt)
+		if err != nil {
+			return nil, fmt.Errorf("failed to decrypt event: %w", err)
+		}
+	}
 	err = evt.Content.ParseRaw(evt.Type)
 	if err != nil {
 		return nil, fmt.Errorf("failed to parse event content: %w", err)