test: add npm caching

Author: sokra

.github/workflows/nodejs.yml

@@ -80,6 +80,18 @@ jobs:
         if: matrix.os == 'windows-latest'
         run: npm i -g npm
 
+      - name: Get npm cache directory
+        id: npm-cache
+        run: |
+          echo "::set-output name=dir::$(npm config get cache)"
+
+      - uses: actions/cache@v1
+        with:
+          path: ${{ steps.npm-cache.outputs.dir }}
+          key: ${{ runner.os }}-node-${{ hashFiles('**/package-lock.json') }}
+          restore-keys: |
+            ${{ runner.os }}-node-
+
       - name: Install dependencies
         run: npm i
 
@@ -124,6 +136,18 @@ jobs:
         if: matrix.os == 'windows-latest'
         run: npm i -g npm
 
+      - name: Get npm cache directory
+        id: npm-cache
+        run: |
+          echo "::set-output name=dir::$(npm config get cache)"
+
+      - uses: actions/cache@v1
+        with:
+          path: ${{ steps.npm-cache.outputs.dir }}
+          key: ${{ runner.os }}-node-${{ hashFiles('**/package-lock.json') }}
+          restore-keys: |
+            ${{ runner.os }}-node-
+
       - name: Install dependencies
         run: npm i