Build Windows executable in shared Steam depot (#50)

## Summary
- install the nightly Windows MSVC target and cargo-xwin in CI
- build the production Windows executable alongside Linux
- package both executables and only imported_assets in one Steam depot

Reviewed-on: #50
Co-authored-by: Álex Román Núñez <eirexe@eirteam.moe>

Cargo.toml

@@ -16,6 +16,7 @@ bevy = { version = "0.19", features = ["asset_processor", "basis-universal", "be
 # Loads the scenes you author in the editor (assets/*.bsn) and builds
 # physics colliders from them. An ordinary dependency; remove it if you
 # stop using authored scenes.
+blake3 = { version = "1.8.5", features = [ "pure" ] }
 thiserror = "2"
 avian3d = "0.7"
 arrayvec = "0.7.8"
@@ -33,7 +34,7 @@ strum = "0.28.0"
 strum_macros = "0.28.0"
 bevy_asset_loader = "0.27.0"
 ron_asset_manager = "0.9.0"
-gc-adapter-neo = { version = "1.1.0", features = ["libusb"] }
+gc-adapter-neo = { version = "1.1.1", features = ["libusb"] }
 rhai = "1.26.0"
 enum_cycling = "0.2.1"
 enum_cycling_derive = "0.2.1"