Publish a vercel.json JSON schema

[bitjson]

Is your feature request related to a problem? Please describe.
I've made plenty of mistakes in now.json files, and I regularly spend a lot of time searching through documentation to try to figure out available options.

Describe the solution you'd like
If Zeit published a JSON schema for now.json, I'd get autocomplete and built-in docs in my IDE.

You can see a live example at ide.bitauth.com. (Click "Import or Restore Template" and try hovering over the default keys.) A lot of compatible IDEs and JSON editing software will automatically start using schemas where available. E.g. try opening test.json:

{ "$schema": "https://bitauth.com/schemas/authentication-template-v0.schema.json" }

in VSCode, then use Ctrl + Space to trigger suggestions.

Describe alternatives you've considered
This is a nice alternative to type-checking now.json with a search engine / combing through docs.

Additional context
Continued from https://github.com/zeit/docs/issues/1200:

For what it's worth, it's actually really easy to generate a schema from TypeScript using ts-json-schema-generator. Here's how I'm using it: https://github.com/bitauth/bitcoin-ts/blob/5d2bd4367468e7c9e07c535cb84723c59b592f5f/package.json#L54

I'm generating this schema from this ts file. TypeScript's tooling makes it extremely easy to work with and update.

[Jianrong-Yu]

There is one here, for anyone have not found it yet

[Jianrong-Yu]

And another one here: https://github.com/ph1p/vercel-vscode-schemes/tree/master/schemas

[gogocharli]

Hello there, we have now published a schema for vercel.json which can be found here: https://openapi.vercel.sh/vercel.json