Add build workflow

.github/workflows/build.yml

@@ -0,0 +1,18 @@
+name: Build
+on: [push, pull_request]
+
+jobs:
+  build:
+    name: Build
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Install .NET 8.0.x
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: "8.0.x"
+
+      - name: Build
+        run: dotnet build -c Release osu.Game.Resources