feature: insert 1st item on accept if nothing was selected

[Rentib]

Currently doing accept while none of the completion items is selected just hides blink. I believe it would make more sense to insert 1st completion item in this situation. I know that there is 'preselect', which kind of achieves that, but it doesnt work in neither 'manual' nor 'auto-insert'.

[groig]

A mix between preselect and auto_insert would be great.

[Rentib]

It doesn't work with auto_insert, because accept gets suppressed or something.
Essentially select_and_accept does only select part if nothing is selected.