Add back caching of npm modules.

Author: m-voit

.github/workflows/js-parser.yml

@@ -14,6 +14,18 @@ jobs:
         with:
           node-version: 14
 
+      - name: Cache node modules as long as os and package-lock.json do not change.
+        uses: actions/cache@v2
+        env:
+          cache-name: cache-node-modules
+        with:
+          path: ~/.npm
+          key: ${{ runner.os }}-test-${{ env.cache-name }}-${{ hashFiles('**/package-lock.json') }}
+          restore-keys: |
+            ${{ runner.os }}-test-${{ env.cache-name }}-
+            ${{ runner.os }}-test-
+            ${{ runner.os }}-
+
       - name: Test js parser.
         working-directory: ./js-parser
         run: |