Set up GitHub action for Doctor (#849)

Summary:
Action for Doctor.
Pull Request resolved: https://github.com/facebook/flipper/pull/849

Test Plan: Watch that box below turn green.

Reviewed By: mweststrate

Differential Revision: D20281213

Pulled By: passy

fbshipit-source-id: 87977c3f67605b4f4f080dd6ca7ab921b10a375b

.github/workflows/nodejs-doctor.yml

@@ -0,0 +1,23 @@
+name: Doctor Node CI
+
+on: [push, pull_request]
+
+jobs:
+  build:
+
+    runs-on: 'ubuntu-latest'
+
+    steps:
+    - uses: actions/checkout@v1
+    - uses: actions/setup-node@v1
+      with:
+        node-version: '12.x'
+    - name: install
+      working-directory: doctor
+      run: yarn
+    - name: test
+      working-directory: doctor
+      run: yarn test
+    - name: run
+      working-directory: doctor
+      run: yarn run run