added 6th kyu, minor improvements

DieJudoGürtelprüfung/kyu.php

@@ -38,7 +38,7 @@ return $pageURL;
 function htmlCardCode($article, $Parsedown){
 	if(
 		empty($article['yaml'])
-		|| empty($article['mdText'])
+		&& empty($article['mdText'])
 	) return "";
 return
 	"<div class=\"col s12 m6\">"
@@ -145,6 +145,7 @@ return
 				$fileNames = [];
 				foreach($fileIterator as $fileInfo){
 					if(!$fileInfo->isFile()) continue;
+					if( $fileInfo->getExtension() != "md") continue;
 					$fileNames[] = $fileInfo->__toString();
 				}
 				sort($fileNames);