Matrix Formatting in JSON.print()

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1

I would like to print a JSON structure which includes nicely formed matrices. The goal is for data to be human-readable. Ideally, the dictionary Dict("matrix" => [1 2 3;4 5 6;7 8 9]) would be printed like,

{
    "matrix" :  [
         [1, 2, 3],
         [4, 5, 6],
         [7, 8, 9]
    ]
}

The default behavior of JSON.jl (using indentations), is to place a newline after every comma in the matrix. This ends up being hard to read data.

Is there a way to customize JSON.Writer.StructuralContext to achieve the desired result?