On startup zsh would call all zsh env scripts (situated in `zsh/env`
or `zsh/env.d/*.zsh`) *and* all sh scripts (in `sh/env` or
`sh/env.d/*.sh`).
However, by that point, those scripts had already been sourced once - so
they just double up startup time.
Add a simple alias to quickly use distrobox with `db` alias, and modify
pure prompt initialization slightly so that it displays a hostname when
in a distrobox container (akin to operating from ssh or normal container
usage).
HACKY implementation makes use of both an internal pure prompt api
(see here https://github.com/sindresorhus/pure/issues/585)
and a distrobox env var that I am not sure how exposed it is either.
Powerlevel10k uses a similar method though, so maybe it is fine
(see here 33916e91a7/internal/p10k.zsh (L8336)).
