Cache root npm folder in GitLab CI

.gitlab-ci.yml

build:
  image: node:10-alpine
  stage: build
  cache:
    key: "$CI_JOB_NAME"
    paths:
      - cache
  except:
    - tags
  before_script:
    - mv cache /root/.npm || echo "No cache found"
    - npm set progress=false
    - npm config set depth 0
  script:
    - npm ci
  after_script:
    - mv /root/.npm cache || echo "No cache found"
  artifacts:
    paths:
      - node_modules
    expire_in: 20 minutes