Add Windows to GitHub Actions CI matrix

Summary: Pull Request resolved: https://github.com/facebook/flipper/pull/741

Reviewed By: jknoxville

Differential Revision: D19371114

fbshipit-source-id: 07c6bd71e58011cc3fffa34354546eb773e3fc3d

.github/workflows/nodejs.yml

@@ -5,11 +5,12 @@ on: [push, pull_request]
 jobs:
   build:
 
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
 
     strategy:
       matrix:
         node-version: [10.x, 12.x]
+        os: ['ubuntu-latest', 'windows-latest']
 
     steps:
     - uses: actions/checkout@v1
@@ -23,5 +24,9 @@ jobs:
       run: yarn lint
     - name: test
       run: yarn test
-    - name: build
+    - name: build linux
+      if: matrix.os == 'ubuntu-latest'
       run: yarn build --linux
+    - name: build windows
+      if: matrix.os == 'windows-latest'
+      run: yarn build --win