Add support for projects managed with Yarn (#13644)

TODO:
- [ ] File a PR with Yarn to add Zed to the list of supported IDEs.

Fixes: https://github.com/zed-industries/zed/issues/10107
Fixes: https://github.com/zed-industries/zed/issues/13706
Release Notes:

- Improved experience in projects using Yarn. Run `yarn dlx
@yarnpkg/sdks base` in the root of your project in order to elevate your
experience.

---------

Co-authored-by: Saurabh <79586784+m4saurabh@users.noreply.github.com>

docs/src/languages/yarn.md

@@ -0,0 +1,8 @@
+# Yarn
+[Yarn](https://yarnpkg.com/) is a versatile package manager that improves dependency management and workflow efficiency for JavaScript and other languages. It ensures a deterministic dependency tree, offers offline support, and enhances security for reliable builds.
+
+## Setup
+
+1. Run `yarn dlx @yarnpkg/sdks base` to generate a `.yarn/sdks` directory.
+2. Set your language server (e.g. VTSLS) to use Typescript SDK from `.yarn/sdks/typescript/lib` directory in [LSP initialization options](../configuring-zed.md#lsp). The actual setting for that depends on language server; for example, for VTSLS you should set [`typescript.tsdk`](https://github.com/yioneko/vtsls/blob/6adfb5d3889ad4b82c5e238446b27ae3ee1e3767/packages/service/configuration.schema.json#L5).
+3. Voilla! Language server functionalities such as Go to Definition, Code Completions and On Hover documentation should work.