Add online fix support for EOS matchmaking games through an injected payload.

[Ran-Mewo]

Some games run multiplayer through EOS instead of Steam. The current 480 trick can't reach that since the EOS traffic never crosses Steam, so the only way to support them is in-process — i.e. a small DLL (OnlineFix.dll) injected into the game by OpenSteamTool on launch.

I've put together a working implementation in #97. The reasonable concern is that this crosses the boundary of "SteamClient-side only" that OpenSteamTool tries to keep, so this poll serves to gauge community interest before deciding whether to merge it (likely as an opt-in / experimental feature rather than on by default).

Maintenance scope

The only piece that meaningfully needs upkeep is EosBridge, which patches a handful of EOS SDK exports:

• EOS_Connect_Login, EOS_Connect_CreateDeviceId
• EOS_Lobby_CreateLobby, EOS_Lobby_JoinLobby, EOS_Lobby_JoinLobbyById (just clearing the bPresenceEnabled field, whose offset is per-struct)
• EOS_IntegratedPlatformOptionsContainer_Add

If any of these are renamed or removed in a future SDK, GetProcAddress returns null, EosBridge aborts before installing any hook, and the game runs without any modifications.

As for the struct layouts:

• A new field added after bPresenceEnabled — everything's fine. Our partial mirror in EosTypes.h stops at that field, so anything past it is simply ignored. The offset we use doesn't change.
• A new field added before bPresenceEnabled — the offset would shift, and the mirror would need the new field added to stay correct. This has never happened in EOS so far; new releases only append at the end.

Everything else (injection, payload boot, process-tree propagation, logging) is OS-level glue that doesn't really change.

[JordanField-GOAT]

Good idea