scala-js: install npm CI action

Author: aslesarenko

.github/workflows/ci.yml

@@ -66,12 +66,18 @@ jobs:
         os: [ubuntu-latest]
         scala: [2.13.8, 2.12.15]
         java: [adopt@1.8]
+        node-version: [16.x]
     runs-on: ${{ matrix.os }}
     steps:
-      - name: Checkout current branch (full)
-        uses: actions/checkout@v2
+      - uses: actions/checkout@v2
+
+      - name: Setup NPM
+        uses: pnpm/action-setup@v2
         with:
-          fetch-depth: 0
+          version: 9.2.0
+          node-version: ${{ matrix.node-version }}
+          cache: "pnpm"
+      - run: pnpm install
 
       - name: Setup Java and Scala
         uses: olafurpg/setup-scala@v10