Support plugins in Playground

Playground is a great application to test Prettier with JavaScript and other supported languages.

Considering the amount of plugins that are currently being developed, a quick way to test how non-supported, non-official plugins behave would be welcome. It would help users preview if the plugin matches their needs, support plugin developers to demonstrate new changes, and follow good practices to report bugs even with plugins.

The code of these non-official plugins usually lives in NPM packages or simply GitHub repositories. In order to have it live in the playground, we would have to either register them and pull it when the playground is built, or at runtime, if we are able to pull them dynamically. I’m suggesting using Turbo for managing packages from the browser.

Before we get into details, would it make sense? I’m interested in contributing this patchset if you think this is a good idea. I’m also taking any design ideas to make this work.

Start by reviewing the Playground implementation and its package-loading or build flow; the issue names no specific files, entry points, or tests. First establish the supported approach for loading non-official plugins, then verify that a plugin can be used in the Playground and that the behavior is covered by appropriate tests.