Add an initial github action. (#324)

* Add a new workflow.

* Update gitignore.

.github/workflows/test.yaml

@@ -0,0 +1,18 @@
+jobs:
+  build:
+    runs-on: ubuntu-18.04
+    strategy:
+      matrix:
+        dotnet: [ '2.2.103', '3.0.100' ]
+    name: Dotnet ${{ matrix.dotnet }} sample
+    steps:
+      - uses: actions/checkout@master
+      - name: Setup dotnet
+        uses: actions/setup-dotnet@v1
+        with:
+          dotnet-version: ${{ matrix.dotnet }}
+      - run: dotnet build
+
+on:
+  pull_request:
+    types: [assigned, opened, synchronize, reopened]

.gitignore

@@ -2,6 +2,7 @@
 .vs
 obj/
 bin/
+**/TestResults
 
 # User-specific VS files
 *.suo