Add 'tmp/cache/webpack-dlls/' to cache for 'webpack-dev-server-job'

Signed-off-by: Rémy Coutable <remy@rymai.me>

.gitlab/ci/frontend.gitlab-ci.yml

@@ -306,10 +306,10 @@ webpack-dev-server:
     key:
       files:
         - yarn.lock
-        - config/webpack.vendor.config.js
-      prefix: "v2"
+      prefix: "v1"
     paths:
       - node_modules/
+      - tmp/cache/webpack-dlls/
   script:
     - source scripts/utils.sh
     - retry yarn install --frozen-lockfile