Add graphql-voyager

[bollwyvl]

Adds graphql-voyager.

• [ ] integrate graphql-codemirror
  • [x] codemirror mode
  • [x] linter
  • [x] highlighting
  • [x] click for docs signal
  • [ ] make work with "stock" JupyterLab Editor
• [ ] integrate graphql-voyager
  • [x] lazy load (4mb :sob: )
  • [x] show voyager for schema
  • [x] subscribe to docs signal
  • [ ] maybe some css (the material is heavy)
• [ ] integrate subscriptions-transport-ws
  • [x] implement subscription request
  • [ ] show different status in URL
  • [ ] highlight of changes?