message: docs: version notices for the GraphiQL readme
diff: > **Breaking Changes & Improvements:** several interfaces are being dropped for new ones for GraphiQL 1.0.0! Read more in [this issue](https://github.com/graphql/graphiql/issues/1165)
  +> **[`graphiql@1.0.0`](https://github.com/graphql/graphiql/milestone/3)** is coming soon & will provide a stable release with react 16, graphql 15 support, fixes, and a headers tab
  +
  +> **[`graphiql@2.0.0-beta`](https://github.com/graphql/graphiql/issues/983)** is a much larger ongoing effort that introduces plugins, i18n, and so many more features after a substantial rewrite using modern react.
  +
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