Merge branch 'c2021' into 'master'

Update copyright for 2021

See merge request postgres-ai/custom-images!26

Author: NikolayS

LICENSE

@@ -630,7 +630,7 @@ state the exclusion of warranty; and each file should have at least
 the "copyright" line and a pointer to where the full notice is found.
 
     Custom Docker Images for PostgreSQL
-    Copyright © 2020, Postgres.ai (https://postgres.ai), Nikolay Samokhvalov
+    Copyright © 2020-2021, Postgres.ai (https://postgres.ai), Nikolay Samokhvalov
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU Affero General Public License as published