Support for Steam on Distrobox

[Heus-Sueh]

Is your feature request related to a problem? Please describe.
If steam is in a container, BoilR will pass the shortcuts of all programs with the wrong command

Wrong:

run --command=bottles-cli com.usebottles.bottles run -b "Gaming" -p "DARK SOULS III"

Right:

distrobox-host-exec flatpak run --command=bottles-cli com.usebottles.bottles run -b "Gaming" -p "DARK SOULS III"

distrobox-host-exec allows the container to invoke the host's flatpak

Describe the solution you'd like
"distrobox-host-exec" before all commands that interact with the host's flatpak

[s-20]

This isn't quite right; Steam needs a "Target" in order to show an icon for the game/app. Instead of moving everything to Launch Options, you should append distrobox-host-exec to the initial flatpak in the Target entry. A la:

(sorry for the Adwaita theming...)

This way, Steam can still apply an icon to the game/app (notice that it vanishes in OP's example pictures...)

I don't know how tricky autodetection would be, but a radio switch in the options menu (something like "is Steam running from a Distrobox Container?") would do wonders, because I feel like anyone running Steam from Distrobox at the very least knows they're doing that.