Add Nushell support

[hustcer]

Thanks for the great tool, could you add Nushell support?
Currently I'm using a custom command to do that:

# Load environment variables from envio profile.
def --env use-env [profile: string, --silent(-s)] {
  let envs = envio list -n $profile -v
    | lines
    | parse '{key}={value}'
    | reduce -f {} { |it, acc| $acc | insert $it.key ($it.value | str trim -c '"') }

  if not $silent { print $envs }
  load-env $envs
}

[humblepenguinn]

Hey @hustcer!

Nushell support is absolutely something we can add to envio.

This is my first time hearing about it and I haven't really used it before so I'm going to need to check it out myself before adding support for it in envio.

Thank you for using envio and if you have any more suggestions or ideas do let me know.