Run build for PRs

Author: timonback

.github/workflows/build.yml

@@ -1,8 +1,12 @@
 name: Build
 
 on:
-  - push
-  - workflow_dispatch
+  push:
+    branches:
+      - master
+  pull_request:
+    types: [ opened, synchronize, ready_for_review ]
+  workflow_dispatch:
 
 permissions:
   contents: write
@@ -16,6 +20,7 @@ jobs:
       - uses: actions/setup-node@v3
         with:
           node-version: 16.x
+          cache: npm
 
       - name: Install dependencies
         run: npm install