Add documentation for mode: "frame"

pages.mdx

@@ -11,7 +11,7 @@
 
 ## Page metadata
 
 Every page starts with frontmatter, the YAML metadata enclosed by `---` at the beginning of a file. This metadata defines how your page appears and behaves.
 
 Use metadata to control:
 
@@ -73,7 +73,7 @@
 
 ### Custom
 
 Custom mode provides a minimalist layout that removes all elements except for the top navbar. Custom mode is a blank canvas to create landing pages or any other unique layouts that you want to have minimal navigation elements for.
 
 ```yaml
 ---
@@ -82,6 +82,17 @@
 ---
 ```
 
+### Frame
+
+Frame mode provides a layout similar to custom mode, but preserves the sidebar navigation. This page mode allows for custom HTML and components while maintaining the default navigation experience. Frame mode is only available for Aspen and Almond themes.
+
+```yaml
+---
+title: "Frame page title"
+mode: "frame"
+---
+```
+
 ### Center
 
 Center mode removes the sidebar and table of contents, centering the content. This is useful for changelogs or other pages where you want to emphasize the content.
@@ -134,7 +145,7 @@
 
 ## Internal search keywords
 
 Enhance a specific page's discoverability in the built-in search by providing `keywords` in your metadata. These keywords won't appear as part of the page content or in search results, but users that search for them will be shown the page as a result.
 
 ```yaml
 ---