Update file .gitlab-ci.yml

.gitlab-ci.yml

 image: node:20.8.0
-
 stages:
   - build
-
-cache:
-  paths:
-    - node_modules/
-
 pages:
   stage: build
+  before_script:
+    - corepack enable
+    - corepack prepare pnpm@latest-9 --activate
+    - pnpm config set store-dir .pnpm-store
   script:
-    - npm install
-    - npm run docs:build
+    - pnpm install
+    - pnpm run docs:build
   artifacts:
     paths:
       - public
     expire_in: 1 day
   only:
     - main
+  cache:
+    key:
+      files:
+        - pnpm-lock.yaml
+    paths:
+      - .pnpm-store