run GHA on pull requests (#8)

Author: aduh95

.github/workflows/ci.yml

@@ -1,14 +1,17 @@
 name: CI
-on: [push]
+on:
+  pull_request:
+    types: [opened, synchronize, reopened, ready_for_review]
+  push:
 jobs:
   build:
     runs-on: ubuntu-latest
     strategy:
       matrix:
         node: ['14', '16', '18']
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions/setup-node@v2
+      - uses: actions/checkout@v3
+      - uses: actions/setup-node@v3
         with:
           node-version: ${{ matrix.node }}
       - run: npm ci