zsh: Add a section that explains `envsecrets.zsh`
zsh: Add a section that explains `envsecrets.zsh`

Keeping the secrets in envsecrets.zsh is quite simple, however the
current setup of the configuration requires a little bit of manual help
if one wants the most ease of use.

This section explains how to change `envsecrets.zsh`'s file permissions
and how to avoid tracking it with git.

PigeonF/.dotfiles