Add info on keywords in frontmatter (Docs) (#576)

Author: devalog

fern/products/docs/pages/customization/frontmatter.mdx

@@ -15,6 +15,7 @@ title: Customize content using frontmatter
 subtitle: Set titles, add meta descriptions, and more 
 slug: frontmatter
 description: Use frontmatter to set the page title, subtitle, slug, meta description, its OpenGraph image, and a URL to suggest edits.
+keywords: frontmatter, seo, customization, metadata
 og:sitename: Your Company Inc.
 og:title: SEO Metadata Title
 ---
@@ -254,7 +255,8 @@ When configuring SEO metadata, ensure your titles and descriptions are unique, d
 ```mdx
 ---
 title: PlantStore API Quick Start
-headline: "Gett Started with PlantStore API | Developer Documentation"
+headline: "Get Started with PlantStore API | Developer Documentation"
+keywords: plants, garden, nursery
 canonical-url: https://docs.plantstore.dev/welcome
 og:site_name: PlantStore Developer Documentation
 og:title: "PlantStore API Quick Start Guide"
@@ -279,6 +281,13 @@ nofollow: false
   Overrides the canonical URL for this page. Must be a full URL including the protocol (i.e. `https://buildwithfern.com/learn/docs/content/frontmatter`)
 </ParamField>
 
+<ParamField path="keywords" type="string" required={false}>
+  Comma-separated string of keywords relevant to the page content (i.e. `plants, garden, nursery`). These keywords help search engines understand the page topic and contributes to search rankings. Use specific, relevant terms that users might search for when looking for the page's content.
+
+  This field accepts only comma-separated strings, not bracketed arrays.
+
+</ParamField>
+
 ### OpenGraph Properties
 <ParamField path="og:site_name" type="string" required={false}>
   The name of your website as it should appear when your content is shared.