Document how to specify SDK version for snippets (Docs) (#788)

Author: devalog

fern/products/docs/pages/api-references/sdk-snippets.mdx

@@ -92,6 +92,22 @@ navigation:
   To display different package names for SDK users versus documentation users, [use overrides files](/api-definitions/overview/overrides#separate-overrides-for-sdks-and-docs). 
 </Note>
 
+<Accordion title="Specify SDK versions (optional)">
+
+You can specify which SDK version to use when generating code snippets.
+
+<CodeBlock title="docs.yml">
+```yaml {4-6}
+navigation:
+  - api: API Reference
+    snippets:
+      python: 
+        package: your-package-name  # <--- needs to match the naming in generators.yml
+        version: your-version number # SDK version to use for snippets
+```
+</CodeBlock>
+</Accordion>
+
 ### Trigger generation
 
 As the final step, trigger your docs generation by running `fern generate --docs` locally or in CI/CD (i.e., GitHub Actions). The SDK snippets will now appear via a drop-down!