Simplify default setup

Most apps don't need to be tested on different OSes

Author: muan

.github/workflows/nodejs.yml

@@ -1,20 +1,11 @@
 name: Node CI
 
-on:
-  pull_request:
-    branches:
-    - master
+on: [push]
 jobs:
   build:
-    runs-on: ${{ matrix.os }}
-
-    strategy:
-      fail-fast: false
-      matrix:
-        os: [ubuntu-latest, windows-latest, macos-latest]
-
+    runs-on: macos-latest
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v2
     - name: Use Node.js 12.x
       uses: actions/setup-node@v1
       with: