Add Native DOSBox support (Feature Request)

Feature Request

Add Native DOSBox to Proton

I confirm:

• that I haven't found another request for this feature.
• that I have checked whether there are updates for my system available that
  contain this feature already.

Description

Extend Proton and/or the Steam Runtime to use native Linux DOSBox for DOS-based games.

Justification [optional]

Wine doesn't offer proper DOS games support. DOSBox is a separate project. Adding it to Proton would allow to integrate patches for controller support amongst other features. Also, add this and all the DOSBox games for Windows will start "just working" via Steam Play on Linux. Easy way to bolster the Steam Play library, benefitting Valve commercially.

However, it may be worth considering adding this to Steam Runtime instead and claiming Linux-native compatibility on all the DOS games. This would bolster the library of games showing as made for SteamOS boosting the native library with very little work and a large return.

Risks [optional]

If applied as a Steam Play solution, customers may think the games rely on Wine.
To mitigate this, apply the change at the Steam Runtime level and mark all the games as Linux-compatible instead without claiming the games need Steam Play to work.

References [optional]

Examples of games that would benefit include:

• DOOM (#1534)
• Worms (#444)

Business Case

See Justification/Risks above. This is a change which if done at the Steam Runtime level, could provide a large ROI for a very minor risk and very little work.

No files, tests, or entry points are named. Start by determining whether Proton or the Steam Runtime should own DOSBox integration, then review related issues #1534 and #444. Done would require an agreed implementation scope and a defined compatibility approach for DOS-based games.