Update copyright information

aleksis/apps/alsijil/apps.py

@@ -10,7 +10,10 @@ class AlsijilConfig(AppConfig):
     }
     licence = "EUPL-1.2+"
     copyright_info = (
+        ([2019, 2020], "Tom Teichler", "tom.teichler@teckids.org"),
         ([2019], "Dominik George", "dominik.george@teckids.org"),
         ([2019], "mirabilos", "thorsten.glaser@teckids.org"),
-        ([2019], "Tom Teichler", "tom.teichler@teckids.org"),
+        ([2020], "Julian Leucker", "leuckeju@katharineum.de"),
+        ([2020], "Jonathan Weth", "wethjo@katharineum.de"),
+        ([2020], "Hangzhi Yu", "yuha@katharineum.de"),
     )