fdo#82969 add global shortcut for autospellcheck

Change-Id: I02b933ac2080ddb46b06a525a0304833ec28acf8
Reviewed-on: https://gerrit.libreoffice.org/13088
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>