Forward serde_json::value::RawValue to serde_json::RawValue

[bheylin]

Given that Value is in the root of the crate I argue that RawValue should be at the same level.

I use RawValue even more than I use Value and I would like to see it promoted, even if that just means
making the import more inviting to use.

[dtolnay]

Thanks for the PR. I would prefer to be pretty selective about what goes in the crate root. Needing RawValue more often than Value is not typical.

[bheylin]

Thanks for the PR. I would prefer to be pretty selective about what goes in the crate root. Needing RawValue more often than Value is not typical.

All good, it was worth a try!