Move local nuget feed to Raylib-cs/nuget and track with .keep

Moved for organisation and using .keep so the local nuget feed can be optional.

.github/workflows/build.yml

@@ -29,11 +29,8 @@ jobs:
             9.0.x
             10.0.x
 
-      - name: Prepare local NuGet source
-        run: mkdir -p nuget
-
       - name: Create NuGet Package
-        run: dotnet pack Raylib-cs -c Release --output nuget
+        run: dotnet pack Raylib-cs -c Release --output Raylib-cs/nuget
 
       - name: Restore + Install Built Package
         run: |
@@ -46,17 +43,17 @@ jobs:
       - name: Upload NuGet Package As Artifact
         uses: actions/upload-artifact@v7
         with:
-          path: nuget/*
+          path: Raylib-cs/nuget/*
 
       - name: Upload NuGet Package As Release
         uses: softprops/action-gh-release@v3
         if: startsWith(github.ref, 'refs/tags/')
         with:
-          files: nuget/*
+          files: Raylib-cs/nuget/*
 
       - name: Publish to NuGet
         if: startsWith(github.ref, 'refs/tags/')
         run: |
           dotnet nuget push \
-            nuget/* \
+            Raylib-cs/nuget/* \
             --api-key ${{secrets.NUGET_API_KEY}}