Merge pull request railwayapp#6 from railwayapp/jr/add-github-ci

Add GitHub CI

.github/workflows/ci.yml

@@ -0,0 +1,32 @@
+name: CI
+
+on: [push]
+
+env:
+  CI: true
+
+jobs:
+  build:
+    name: Build
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Use Node 12
+        uses: actions/setup-node@v1
+        with:
+          node-version: 12.x
+
+      - uses: actions/cache@v2
+        with:
+          path: "**/node_modules"
+          key: ${{ runner.os }}-modules-${{ hashFiles('**/yarn.lock') }}
+
+      - name: Install packages
+        run: yarn install
+
+      - name: Build
+        run: yarn build
+