fix(graphiql): update graphiql playground to latest version

[juliankoehn]

This PR migrates GraphiQL to v5 following the official migration guide:
https://github.com/graphql/graphiql/blob/main/docs/migration/graphiql-5.0.0.md

relates graphql/graphiql#4034

[endigma]

Hi @juliankoehn, thanks for your contribution! We'll put this in the queue for a review, in the meantime, can you do a few things:

• Update the branch to current master, rebase or merge are both fine
• Check if subscriptions work correctly in the new version? We used to have a bit of code to make them work that appears to have been removed, is it unnecessary in the new version?