Exclude hidden files and directories when synchronizing via Rsync

Exclude hidden files and directories when synchronizing via Rsync

According to RFC 9286 section 4.2.2, filenames in the RPKI cannot start
with a dot. And RFC 6481 section 1.1 describes the concept of a publication
point as a "directory in a publicly accessible filesystem". From there it
follows there is no need to transfer hidden files and directories. This may
help in avoiding exposure to intermediate states (e.g., /a/.~tmp~/b.roa).