japanese/canna-server: Update to 3.8
Add the documents to be installed.
Add post-install-DOCS-on.
Update pkg-descr.
https://raw.githubusercontent.com/canna-input/canna/refs/tags/release-3.8/ChangeLog
PR: 295142
Co-authored-by: AIDA Shinra <shinra@j10n.org>
Approved by: fluffy (mentor)