[Suggestion] provide default prompt for fish shell

[scarf005]

Is your feature request related to a problem? Please describe.

it's easy to distinguish you're inside a box on bash thanks to a custom prompt like 📦[scarf@fedora scarf]$:

distrobox/distrobox-init

Lines 2028 to 2031 in c05b6a4

	if [ -f /run/.toolboxenv ]; then
	[ "\${BASH_VERSION:-}" != "" ] && PS1="📦[\u@\$CONTAINER_ID \W]\$ "
	[ "\${ZSH_VERSION:-}" != "" ] && PS1="📦[%n@\$CONTAINER_ID]%~%# "
	fi

however there isn't one for fish, making it hard to determine whether you're on host or box.

Describe the solution you'd like

provide default fish shell prompt inside distrobox.

Describe alternatives you've considered

provide guide on how to set up custom fish prompt that detects whether you're inside a box and shows prompt accordingly.

Additional context

i'm interested in opening a PR.

[89luca89]

Thanks @scarf005 i'm open to contributions on this, I have no experience at all with fish shell

[Boria138]

Thanks @scarf005 i'm open to contributions on this, I have no experience at all with fish shell

#1588