feat(playground): Add JSON support

[MichaReiser]

Summary

This PR adds basic JSON support to the playground. It's not the deluxe version.

To use JSON, it's necessary to switch to the multifile mode and change the extension to json.

We should probably add a language dropdown in the future that lets you pick JavaScript, TypeScript, or JSON, similar to what Prettier has. I decided not to do this as part of this PR because it's mainly to unlock the development of the JSON formatter and not to promote the JSON formatting on the playground.

Test Plan

I tested the playground with a JSON, jS ,and TypeScript file

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[MichaReiser]

I moved this to the prettierWorker to remove the prettier dependencies from the main bundle.

[ematipico]

I just tried to parse a JSON file, but prettier formatter emits an error

[MichaReiser]

I just tried to parse a JSON file, but prettier formatter emits an error

Thanks. Should now be fixed!

[ematipico]

Here's some feedback:

• prettier now handles JSON files;
• if you create a .json file and tick TypeScript or JSX under "Source Type", the extension of the file changes;
• from the previous step, if you untick the option, the file now has .js extension

[MichaReiser]

Here's some feedback:

* prettier now handles JSON files;

* if you create a `.json` file and tick `TypeScript` or `JSX` under "Source Type", the extension of the file changes;

* from the previous step, if you untick the option, the file now has `.js` extension

These are good points. I'll create an issue for updating the playground to add proper support for different languages (hide language and formatter options that aren't relevant)