Add json schema of fixture runner options

[JLHwung]

Q	A
License	MIT

Add basic JSON schema of Babel fixture runners. Configure json.schemas so that it works on VSCode.

Note that currently /data/schema.json will be published to npm. I am either good with publishing or not.

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/52423/

[JLHwung]

This schema was generated from typings/babel-parser.d.ts by https://github.com/YousefED/typescript-json-schema. I have tuned a little bit: replacing minItems: 2, maxItems: 2 to additionalItems: false.

We should explore generating API option types from JSON schema or vice.

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babel-plugin-multi-config	Configuration

[JLHwung]

This one is from my local config. I can remove it if you have different choices here. 😄

[nicolo-ribaudo]

Yup, I have my own vscode config and the main reason I "ignored" this PR is that I was annoyed that it contained its own config, sorry 😅

We can rename it to settings.example.json, and have this in our .gitignore:

.vscode
!.vscode/settings.example.json

and then in CONTRIBUTING.md mention that we have that example vscode config.

[liuxingbaoyu]

microsoft/vscode#40233

Yes, it looks like VS Code supports this a bit badly.

[liuxingbaoyu]

Amazing work! Looking forward to it being merged.

[nicolo-ribaudo]

I updated the PR to do #12619 (comment), and added a few lines to CONTRIBUTING.md to explain how to setup the editor.

We can iterate in a follow-up PR if we want to automatically generate the parser schema file!