docs: add YAML schema validation for product.yml and generators.yml (#3506)

Co-authored-by: fern-api[bot] <115122769+fern-api[bot]@users.noreply.github.com>
Co-authored-by: Devin Logan <devinannlogan@gmail.com>

Author: 3 people

fern/products/docs/pages/navigation/products.mdx

@@ -52,11 +52,14 @@ You can also define external products, which link to external URLs (separate app
   </Folder>
 </Files>
 
-<Note>No separate yml file needed for external products</Note>
+<Tip>
+  To enable YAML validation and autocompletion in your editor, add a schema directive to the top of each `product.yml` file.
+</Tip>
 
 <CodeBlocks>
 <CodeBlock title="products/product-a.yml">
 ```yaml
+# yaml-language-server: $schema=https://raw.githubusercontent.com/fern-api/fern/main/product-yml.schema.json
 navigation: 
   - section: Introduction
     contents:
@@ -68,6 +71,7 @@ navigation:
 <CodeBlock title="products/product-b.yml">
 
 ```yaml
+# yaml-language-server: $schema=https://raw.githubusercontent.com/fern-api/fern/main/product-yml.schema.json
 tabs: 
   api: 
     title: API Reference

fern/products/sdks/reference/generators-yml-reference.mdx

@@ -6,7 +6,12 @@ max-toc-depth: 3
 
 The `generators.yml` file serves two purposes: it declares your API definition (required for OpenAPI/AsyncAPI), and configures SDK generation, including which languages to generate, where to publish them, and how to customize each SDK.
 
+<Tip>
+  To enable intelligent YAML validation and autocompletion in your editor, add a schema directive to the top of your `generators.yml` file.
+</Tip>
+
 ```yaml title="generators.yml" maxLines=10
+# yaml-language-server: $schema=https://schema.buildwithfern.dev/generators-yml.json
 api:
   specs:
     - openapi: "./openapi.yml"