Replace deprecated Antigen Zsh plugin manager

[Bruno Semperlotti]

Antigen plugin manager is a dead project, it has no commit since 5 years
zsh-users/antigen#725

One annoying issue is that loading antigen.zsh breaks zsh completions : zsh-users/antigen#603

It must be replaced by another plugin manager or manage plugins manually

• https://github.com/marlonrichert/zsh-snap
• https://github.com/zplug/zplug
• https://github.com/zdharma-continuum/zinit

[Bruno Semperlotti]

Best option seems to be: https://github.com/mattmc3/antidote