add format check action

.github/workflows/format.yml

@@ -0,0 +1,16 @@
+name: Format check
+on:
+  push:
+
+jobs:
+  format_check:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v4
+      - name: Setup .NET Core
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: 8.0.x
+      - name: Check formatting
+        run: dotnet format whitespace ./ArtNet-Unity.sln --verify-no-changes