NEWS: notmuch insert, search updates

News for

- cli: add support for notmuch search --duplicate=N with --output=messages
- cli/insert: add post-insert hook
- cli/insert: require succesful message indexing for success statu
NEWS: functions in emacs notmuch-show-stash-mlarchive-link-alist

News for emacs: allow functions in
notmuch-show-stash-mlarchive-link-alist.