[feature] Add shell completions

[Freed-Wu]

Just change Makefile to install /usr/share/zsh/site-functions/_has:

#compdef has

_arguments -s -S \
  -q'[Silent mode]' \
  {-h,--help}'[Display this help text and quit]' \
  {-V,--version}'[Show version number and quit]' \
  '*: :{_command_names -e}'

❯ has -<TAB>
external command
option
-h          Display this help text and quit
--help      Display this help text and quit
-q          Silent mode
--version   Show version number and quit
-V          Show version number and quit
❯ has -q <TAB>
external command
7za                                 A file archiver with highest compression ratio
7z                                  A file archiver with highest compression ratio
7zr                                 A file archiver with highest compression ratio
a2ping                              convert between PS, EPS and PDF and other page description formats
a52dec                              decode ATSC A/52 audio streams
...

TIA.