Update build.yml

.github/workflows/build.yml

@@ -1,16 +1,31 @@
-name: Build JavaScript assets
+name: JavaScript
 
 on:
-    push:
-        branches:
-            - master
+  push:
+    branches:
+      - master
 
 jobs:
-    build:
-        runs-on: ubuntu-latest
+  build:
+    name: JS / Build
+    runs-on: ubuntu-latest
 
-        steps:
-            - uses: actions/checkout@master
-            - uses: flarum/action-build@master
-              env:
-                  GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+    steps:
+      - name: Check out code
+        uses: actions/checkout@v2
+
+      - name: Restore npm cache
+        uses: actions/cache@v2
+        with:
+          path: ~/.npm
+          key: ${{ runner.os }}-node-${{ hashFiles('js/package-lock.json') }}
+          restore-keys: |
+            ${{ runner.os }}-node-
+      # Flarum action will install npm, cd into `./js`, run `npm run build` and
+      # `npm run build-typings`, then commit and upload any changes
+      - name: Build production JS
+        uses: flarum/action-build@2
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          build_script: build
+          package_manager: npm