encoding/json: add ... json tag to spread it in struct

[maru44]

I added new json tag.
This can be instead of embedded generics.

As you know, we cannot embed generics to struct.

this is invalid

type bad[T any] struct{
    Name string
    T
}

I want use embed in json, so I added new json tag to spread struct in its parent.

ex)

type good[T any] struct {
    Name string
    Free T `json:"..."`
}

type more struct {
    Age int
    Country string
}

var foo = good[more]{
    Name: "Foo",
    more: more{
        Age: 20,
        Country: "U.S.A",
    },
}

If you encode it in json. It'll be like this.

{"Name": "Foo", "Age": 20, "Country": "U.S.A"}

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Message from Daniel Martí:

Patch Set 1: Code-Review-2

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Message from Russ Cox:

Patch Set 1: Hold+1

(1 comment)

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[mvdan]

Closing per the CL comments - this needs a proposal, but one hasn't been filed yet.