Added custom 404 page documentation (#1123)

* Update settings/custom-404-page.mdx

* Update docs.json

* add icon

* move to guides

* copy edit

* remove duplicate example

* consolidate best practices in the intro

* change heading level

---------

Co-authored-by: mintlify[bot] <109931778+mintlify[bot]@users.noreply.github.com>
Co-authored-by: Ethan Palm <56270045+ethanpalm@users.noreply.github.com>

Author: mintlify[bot]

docs.json

@@ -144,6 +144,7 @@
               "guides/changelogs",
               "guides/hidden-pages",
               "settings/broken-links",
+              "settings/custom-404-page",
               "guides/monorepo",
               {
                 "group": "Custom Subdirectory",

settings/custom-404-page.mdx

@@ -0,0 +1,41 @@
+---
+title: "Custom 404 page"
+description: "Customize the title and description of your 404 error page"
+icon: "file-warning"
+---
+
+You can control the title and description of the 404 error page that appears when users navigate to broken or missing links.
+
+When customizing your 404 page, use the description to guide users to helpful resources or links in your documentation that can help them find what they're looking for.
+
+## Configuration
+
+Configure your 404 page in the `errors.404` section of your `docs.json` file:
+
+```json
+"errors": {
+  "404": {
+    "redirect": false,
+    "title": "I can't be found",
+    "description": "What ever **happened** to this _page_?"
+  }
+}
+```
+
+## Parameters
+
+<ResponseField name="redirect" type="boolean">
+  Whether to automatically redirect to the home page when a page is not found.
+  
+  Set to `true` to redirect to the home page.
+
+  Set to `false` to show the custom 404 page.
+</ResponseField>
+
+<ResponseField name="title" type="string">
+  Custom title for the 404 error page. This replaces the default "Page not found" heading.
+</ResponseField>
+
+<ResponseField name="description" type="string">
+  Custom description for the 404 error page. Supports Markdown formatting.
+</ResponseField>