Support prettier key as a configuration option in package.json

[yeskunall]

Prettier supports passing prettier as a key to package.json (or package.yml). It is actually the first thing it checks, based on the order of precedence.

It would be great if prettierd also supported this.

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Thanks for working on this! 💖

[fsouza]

hmm I thought this would just work? Under the hood, prettierd is invoking prettier's resolveConfig and I assumed that supported package.json, but probably not hah