Support the HTTP QUERY method (RFC 10008)

Support for the HTTP QUERY method ([RFC 10008](https://datatracker.ietf.org/doc/html/rfc10008)) is being worked on upstream, both in the GraphQL spec and in Go:

https://github.com/graphql/graphql-over-http/pull/411 — adds QUERY to the GraphQL-over-HTTP specification.
https://github.com/golang/go/issues/80058 — adds http.MethodQuery to net/http.

gqlgen currently has transport.GET and transport.POST but no transport for QUERY, so QUERY requests are rejected with transport not supported.

I think it’s fine to revisit this in gqlgen once support for the GraphQL specification and Go query methods has been released.

查看 transport package 中现有的 transport.GET 和 transport.POST 实现，以了解其模式。作为上下文，已链接 upstream GraphQL-over-HTTP spec PR 和 Go net/http issue。添加新的 transport.QUERY handler 将涉及检查 Go 版本是否支持 http.MethodQuery，并更新 router 以接受使用 QUERY 方法的 requests。向 GraphQL endpoint 发起 QUERY requests 进行测试。

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