Update documentation copyright.
@@ -74,7 +74,7 @@ RESOURCES = \
DOCFLAGS = \
--author "Michael R Sweet" \
- --copyright "Copyright (c) 2020-2021 by Michael R Sweet" \
+ --copyright "Copyright (c) 2020-2022 by Michael R Sweet" \
--docversion $(PAPPL_VERSION)
.SUFFIXES: md
