Fixup ctags-complete command to search for partial matches for the
current selection in all tags files listed in ctagsfiles option. Format
the results to fit the Kakoune completions type.
Add ctags-enable-autocomplete and ctags-disable-autocomplete commands to
add and remove an InsertIdle hook to select the previous word and call
ctags-complete.
Use the ctags_min_chars option to limit the noise of returning many
completions for very short selections.