build: CI: add caching for Windows too (#253)

Co-authored-by: Justin Beckwith <beckwith@google.com>

Author: XhmikosR

.github/workflows/ci.yaml

@@ -37,6 +37,18 @@ jobs:
       - uses: actions/setup-node@v2
         with:
           node-version: ${{ env.NODE }}
+      - name: Get npm cache directory
+        id: npm-cache
+        run: |
+          echo "::set-output name=dir::$(npm config get cache)"
+      - name: Set up npm cache
+        uses: actions/cache@v2
+        with:
+          path: ${{ steps.npm-cache.outputs.dir }}
+          key: ${{ runner.os }}-node-v${{ env.NODE }}-${{ hashFiles('package.json') }}-${{ hashFiles('package-lock.json') }}
+          restore-keys: |
+            ${{ runner.os }}-node-v${{ env.NODE }}-${{ hashFiles('package.json') }}-${{ hashFiles('package-lock.json') }}
+            ${{ runner.os }}-node-v${{ env.NODE }}-
       - run: npm ci
       - run: npm test
   lint: