Create nodejs workflow (#555)

Summary:
A very basic first workflow that we can extend to match what we currently have in Travis and hopefully remove that in the near future.
Pull Request resolved: https://github.com/facebook/flipper/pull/555

Test Plan: https://github.com/facebook/flipper/pull/555/checks?check_run_id=232330215

Reviewed By: danielbuechele

Differential Revision: D17525516

Pulled By: passy

fbshipit-source-id: c1ebc1af2260482cfa97faae99f3baa5d5b9046c

.github/workflows/nodejs.yml

@@ -0,0 +1,23 @@
+name: Node CI
+
+on: [push]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        node-version: [10.x, 12.x]
+
+    steps:
+    - uses: actions/checkout@v1
+    - name: Use Node.js ${{ matrix.node-version }}
+      uses: actions/setup-node@v1
+      with:
+        node-version: ${{ matrix.node-version }}
+    - name: yarn install, build, and test
+      run: |
+        yarn
+        yarn test