Github action for Jest (#26)

.github/workflows/main.yml

@@ -0,0 +1,18 @@
+name: Jest
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install dependencies
+        run: npm install
+      - name: Run tests
+        run: npm test