[FEATURE REQUEST] - Prefix (compatibility data) location change setting

[Calslock]

What problem does the feature request solve? r2modman assumes prefix (compatibility data) for specific game is placed in the same SteamLibrary location, as it is usually the case on majority of Linux systems. However on Steam Deck, while games can be stored either on internal SSD or SD cards, all prefixes are stored on internal SSD (/home/deck/.local/share/Steam/steamapps/compatdata). Same issue as #943.

Example mock-up (optional)

• New value in Settings -> Locations tab, where compatdata folder for the game can be changed;
• Checkbox "Check for compatdata in Steam directory".

Additional information (optional) It is currently possible to workaround this issue by symlinking compatdata directory from Steam directory onto SD card: ln -s /home/deck/.local/share/Steam/steamapps/compatdata /run/media/mmcblk0p1/steamapps

[WORMSTweaker]

Bumping this because this isn't only a feature that would be good on the deck, but in general for all systems

Not being able to switch around the compat data folder literally locks me out of modding right now, because r2modman thinks my compat folder is on another disk, even though said folder never existed in the first place