Add Yarn 2 section to FAQ

[Rich-Harris]

#993.

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[TrySound]

Yarn 3 fixes the problem
https://github.com/yarnpkg/berry/blob/master/CHANGELOG.md#300-rc1

[merceyz]

Suggested change

	### Does it work with Yarn 2?
	### Does it work with Yarn PnP?

Yarn 1 and pnpm support PnP

[merceyz]

Suggested change

Sort of. The Plug'n'Play feature, aka 'pnp', is broken (it deviates from the Node module resolution algorithm, and doesn't work with native JavaScript modules which SvelteKit — along with an [increasing number of packages](https://blog.sindresorhus.com/get-ready-for-esm-aa53530b3f77) — uses). You can use `nodeLinker: 'node-modules'` in your [`.yarnrc.yml`](https://yarnpkg.com/configuration/yarnrc#nodeLinker) file to disable pnp, but it's probably easier to just use npm or [pnpm](https://pnpm.io/), which is similarly fast and efficient but without the compatibility headaches.

Sort of. The Plug'n'Play feature, aka 'pnp', [doesn't work with native JavaScript modules yet](https://github.com/yarnpkg/berry/issues/638) which SvelteKit — along with an [increasing number of packages](https://blog.sindresorhus.com/get-ready-for-esm-aa53530b3f77) — uses). You can use `nodeLinker: 'node-modules'` in your [`.yarnrc.yml`](https://yarnpkg.com/configuration/yarnrc#nodeLinker) file for Yarn 2+ to use the `node_modules` layout instead.

[Rich-Harris]

Yarn 3 fixes the problem

A Yarn maintainer confirmed that this isn't the case, at least not yet.

@merceyz thank you for the review. We stand by the wording here though — PnP is broken if the threshold is parity with Node's default behaviour, for the two reasons given. It's true that it's possible to disable PnP, but as long as it's the default it will continue to cause confusion in the JS ecosystem. As maintainers who have been affected by that confusion we feel that the recommendation to use alternative package managers is justified.

[avarun42]

Is this still true after PRs yarnpkg/berry#2161 and yarnpkg/berry#3667 got merged? From a cursory glance it seems like PnP supports ES Modules now — can anyone confirm if that means Yarn 3.1+ work with SvelteKit? @Rich-Harris

[dummdidumm]

We don't use yarn, but you are welcome to try it out and report back if it works now