ci: Run on pull requests, and up to node v17

A lot of mistakes I made in recent PRs could have been avoided with
this.

Author: joeyparrish

.github/workflows/nodejs.yml

@@ -1,13 +1,14 @@
 name: Node CI
-on: [push]
+on: [push, pull_request]
 
 jobs:
   build:
     runs-on: ubuntu-latest
 
     strategy:
       matrix:
-        node-version: [4.x, 6.x, 8.x, 10.x, 12.x]
+        node-version: [4.x, 6.x, 8.x, 10.x, 12.x, 14.x, 16.x, 17.x]
+      fail-fast: false
 
     steps:
     - uses: actions/checkout@v1