Upgrade Ariadne (Moving away from GraphQL Playground to GraphiQL2)

[bilalebi]

This branch was merged to develop for experimental purposes
A new branch will be created later to clean up the code and add the proper link to the help page.

Changes

• Upgraded Ariadne to 0.19.1 which uses GraphiQL2 as default API explorer
• Activated the docs explorer which helps with constructing queries and gives an idea of the schema we've got.
• Added a header to the GraphiQL endpoint with Ensembl logo and a link to the help page.

GraphQL Playground has been retired; There was a discussion about this on Ariadne repo, and GraphiQL2 started to be used as default API explorer since 0.18.0.

Comment regarding GraphiQL2 (Their live demo):

• I noticed that settings (JSON format that can be edited) and Schema tab are missing (I asked about the Schema here).
• Many feature will be implemented in the future (Roadmap) for example: Implement new docs explorer (Example with plugins).
• Discussion page: https://github.com/graphql/graphiql/discussions