CI: Github Actions (stripe#1121)

.github/workflows/main.yml

@@ -0,0 +1,41 @@
+# This is a basic workflow to help you get started with Actions
+
+name: CI
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        node: [ '10', '12', '14' ]
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Setup node
+        uses: actions/setup-node@v2
+        with:
+          node-version: ${{ matrix.node }}
+
+      - name: Get yarn cache directory path
+        id: yarn-cache-dir-path
+        run: echo "::set-output name=dir::$(yarn cache dir)"
+
+      - uses: actions/cache@v2
+        id: yarn-cache
+        with:
+          path: ${{ steps.yarn-cache-dir-path.outputs.dir }}
+          key: ${{ runner.os }}-yarn-${{ hashFiles('**/yarn.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-yarn-
+
+      - name: Lint, typecheck, and test
+        run: yarn && yarn test