[graphql-playground-react] multiple rows tab bar

[fcannizzaro]

Changes proposed in this pull request:

• add a new setting tabs.multipleRows to split the single tab bar in multiple rows.

Please let me know if you have any concerns. Thanks!

[linux-foundation-easycla[bot]]

The committers are authorized under a signed CLA.

• :white_check_mark: Francesco Saverio Cannizzaro (b03051b7c0b9c7c7fdbfb5427a09292b6ffbf927)

[acao]

Very cool! I like that it's opt-in