add permission to sd-card dir for steam deck

[renner0e]

Right now when you launch protontricks on steam deck and install games on a sd-card it needs permissions for this directory
/run/media/deck/UUID-of-sd-card

Protontricks gives the correct flatpak override command however when you use multiple sd-cards and swap them out on a regular basis to play different games the uuid will change and you'd have to do a slightly different flatpak override command for every sd- card you plug in.

This will of course also remove that first initial step of pasting the flatpak override command and it is easier to get started for steam deck users.

[flathubbot]

Started test build 142832

[flathubbot]

Build 142832 failed

[renner0e]

oh wait we can't give permission to stuff with absolute paths unless we give filesystem=host
https://docs.flatpak.org/en/latest/sandbox-permissions.html#external-drive-access

[Matoking]

Yeah, the current situation is pretty janky. Flatpak/Freedesktop.org portals don't have support for proper "do you want to grant access to directory X" prompts which would probably be the best way to resolve this. Adding overly broad default permissions might also not be suitable for Flathub apps, though I don't know where exactly that line is drawn.

Anyway, you should be able to just chop the SD card UUID off the path in the flatpak command that Protontricks prints.