feat(ci): add dotnet format check action

.github/workflows/dotnetformat.yml

@@ -0,0 +1,17 @@
+name: Format check on pull request
+on: [push, pull_request]
+jobs:
+  dotnet-format:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v2
+
+      - name: Add dotnet-format problem matcher
+        uses: xt0rted/dotnet-format-problem-matcher@v1
+
+      - name: Restore dotnet tools
+        uses: xt0rted/dotnet-tool-restore@v1
+
+      - name: Run dotnet format
+        uses: xt0rted/dotnet-format@v1