feat: add json format config

[kitimark]

Hello guys.

I'd like to propose add json format config into snaps.Config. for custom json formatting when take the snapshot.

example json format config

 s := snaps.WithConfig(
    snaps.JSON(snaps.JSONConfig{
      Width:    80,
      Indent:   "    ",
      SortKeys: false,
    }),
  )

s.MatchJSON(t, value)
s.MatchStandaloneJSON(t, value)

[gkampitakis]

Hey 👋 Thanks for this contribution. I think it's a good addition will take some time to review it 😄

[gkampitakis]

LGTM