Adds GitHub CI to automate merge test runs

Author: NeedleInAJayStack

.github/workflows/test.yml

@@ -0,0 +1,21 @@
+name: Test
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+jobs:
+  build:
+    name: Build and test on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [macos-latest, ubuntu-latest]
+    steps:
+      - uses: actions/checkout@v2
+      - uses: fwal/setup-swift@v1
+      - name: Build
+        run: swift build
+      - name: Run tests
+        run: swift test