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)).
Marty Oehme