Accessibility#9196 (#1319)

## What/Why

- Screen reader does not announce the search result information as `No
results` on providing invalid input

## Changes

-
[`src/components/search.js`](https://github.com/npm/documentation/pull/1319/files#diff-995f95946b0cbf613b5cf5d8d6335cb1612dcb31907922cd5da28be90a6ff442)

> Add `aria-live` as `polite` to Box element

> Add `announce` function to trigger screen reader announcing the `No
results` message when there is no search result

## Before

![image](https://github.com/user-attachments/assets/5067f434-b86b-4383-899f-fe88b808abac)

## After

- The screen reader announces the search result information as `No
results` on providing invalid input

## References

- github/accessibility-audits#9196

Author: maitxn

src/components/search.js

@@ -10,12 +10,17 @@ import {LightTheme} from '../theme'
 import {LinkNoUnderline} from './link'
 import * as getNav from '../util/get-nav'
 import omit from '../util/omit'
+import {announce} from '../util/aria-live'
 
 const SearchResults = ({results, getItemProps, highlightedIndex}) => {
   const siteMetadata = useSiteMetadata()
-
   if (!results || results.length === 0) {
-    return <Box sx={{fontSize: 2, px: 3, py: 3}}>No results</Box>
+    announce('No results')
+    return (
+      <Box sx={{fontSize: 2, px: 3, py: 3}} aria-live="polite">
+        No results
+      </Box>
+    )
   }
 
   return (