Handle Jhdt as a form of century in time splitter

Close #9

src/NodaTimeSplitter.php

@@ -903,7 +903,7 @@ final class NodaTimeSplitter {
         $bcBceIndicator = '+';
 
         // 17. Jahrhundert
-        if (\preg_match("/^[0-9]{2}\.\ (Jh\.|Jahrhundert|sz|század)$/", $datum)) {
+        if (\preg_match("/^[0-9]{2}\.\ (Jh\.|Jhd(|\.)|Jhdt(|\.)|Jahrhundert|sz|század)$/", $datum)) {
             if ($centuryNo = \intval(\substr($datum, 0, 2))) {
                 $centuryNo--;
                 return [(string)$centuryNo . "01", \strval($centuryNo + 1) . "00", "00", "00", $bcBceIndicator, ""];