Update CONTRIBUTORS.txt

RudolfCardinal · web-flow · commit 1a503366d86e · 2021-05-04T11:59:48.000+01:00
diff --git a/CONTRIBUTORS.txt b/CONTRIBUTORS.txt
@@ -144,3 +144,4 @@ Contributors
 - Stanisław Pitucha, 2020/06/30
 - Lele Gaifax, 2020/08/22
 - Geoffrey T. Dairiki, 2020/08/24
+- Rudolf N. Cardinal, 2021/05/04
