ci: add caching of npm modules

.github/workflows/main.yml

@@ -13,6 +13,14 @@ jobs:
       - uses: actions/setup-node@v4
         with:
           node-version: "lts/*"
+      - uses: actions/cache@v4
+        with:
+          path: |
+            ~/.npm
+            **/node_modules
+          key: ${{ runner.os }}-npm-${{ hashFiles('**/package-lock.json') }}
+          restore-keys: |
+            ${{ runner.os }}-npm
       - run: npm ci
       - run: npm run build:data
       - run: npm run build