chore(docs): add example of landing page (#5205)

* add landing-page schema

* add example of landing page

* chore(docs): update example to VapiAI

* fix(docs): use accesible linking practices

---------

Co-authored-by: Danny Sheridan <83524670+dannysheridan@users.noreply.github.com>
Co-authored-by: Deep Singhvi <deep@buildwithfern.com>

fern/pages/docs/getting-started/global-configuration.mdx

@@ -409,4 +409,7 @@ landing-page:
 
 <ParamField path="path" type="string" required={true}>
   Relative filepath to the desired landing page Markdown file. 
-</ParamField>
+</ParamField>
+
+See [VapiAI's landing page live](https://docs.vapi.ai/welcome) and the associated [Markdown file](https://github.com/VapiAI/docs/blob/main/fern/welcome.mdx?plain=1).
+