feat: Direnv + Devbox support

[pawamoy]

In .envrc:

# Automatically sets up your devbox environment whenever you cd into this
# directory via our direnv integration:

eval "$(
    devbox generate direnv --print-envrc ||
    echo echo Install Devbox: https://www.jetpack.io/devbox/docs/installing_devbox/#install-devbox
)"

# check out https://www.jetpack.io/devbox/docs/ide_configuration/direnv/
# for more details