Add CI

.github/workflows/main.yml

@@ -0,0 +1,23 @@
+name: CI
+
+on:
+  push:
+    branches: [ master ]
+
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v1
+        with:
+          dotnet-version: 5.0.101
+
+      - name: Build
+        run: dotnet build