Add package.json > biome config support

[chneau]

Prettier configuration can be set in package.json instead of creating "yet" another file in the root of the project.
I believe in VSCode, when you have the prettier extension, you get the autocompletion on package.json>prettier.

Would it be nice to have the same UX for biome?

(Couldn't transfer from https://github.com/biomejs/biome-vscode/discussions/169)

[arendjr]

Hah, I think I transferred it at the same time as you created this one.

[arendjr]

I’ll close as duplicate.