Problem: Vim doesn't highlight to be inserted text when completing
Solution: Add support for the "preinsert" 'completeopt' value
(glepnir)
Support automatically inserting the currently selected candidate word
that does not belong to the latter part of the leader.
fixes: vim/vim#3433closes: vim/vim#16403edd4ac3e89
Co-authored-by: glepnir <glephunter@gmail.com>