feat: support Hollow Knight Replay

[Shichien]

Structural Refactor for Hollow Knight and Silksong

This PR restructures ReplayTimerMod into a cleaner dual-platform layout for both Hollow Knight and Silksong.

Thanks to the author's project. In the speedrun community, several people felt it could also serve as a useful tool for Hollow Knight practice. Considering that Team Cherry reused a large amount of Hollow Knight's code when developing Silksong, I think some of the logic might also be reusable. Through a period of Vibe Coding and Tests, I have successfully run this Mod on Hollow Knight, so I submit the PR.

I'm not a native English speaker, so I hope this fairly large PR is still clear enough. I also hope it can be useful for future speedrun practice. If your intention is to keep the ReplayTimer repo only for Silksong, I completely understand. In that case, I can fork it.

Scope Notes

• Intended behavior of replay recording/playback remains unchanged.
• Main impact is structural: project layout, platform boundaries, and startup safety.

What Changed

• Flattened repository structure by removing the nested ReplayTimerMod root layout.
• Moved shared runtime code into src/General and src/General/UI.
• Added platform project and entrypoint:
  • src/HollowKnight
  • src/Silksong

Build

• dotnet build src/Silksong/ReplayTimerMod.SS.csproj -c Release
• dotnet build src/HollowKnight/ReplayTimerMod.HK.csproj -c Release

Preview

[AdiPrk]

Hello Shichien, thank you for these additions to the mod! I've reviewed and tested it, and everything seemed to work well. Merging this in!