This changes the defaults:
- AUTOENV_ENV_FILENAME: .env_auth => .autoenv_auth
- AUTOENV_FILE_ENTER: .env => .autoenv.zsh
- AUTOENV_FILE_LEAVE: .env_leave => .autoenv_leave.zsh
`.env` is usually used only for key-value pairs for environment
settings, e.g. with foreman. We do not want to interfere with this.
Fixes https://github.com/Tarrasch/zsh-autoenv/issues/31.
This is not really necessary, except for the convenience of being in the
.env file's directory during the hook.
But it messes around with the "cd history", e.g. `cd -`!
To reference the .env file or its directory, `$autoenv_env_file` and
`${autoenv_env_file:h}` can be used instead.
