Feature Request: Display a "Featured" Badge for Posts with Specific Meta Key in Jetpack Instant Search Results

### Impacted plugin

Search

### What

Introduce the capability in Jetpack Instant Search to display a "Featured" badge for search results with a specific meta key-value pair

### How

### Description
A user implementing Jetpack Instant Search on their website has expressed the need to enhance the search results. They wish to display a "Featured" badge next to search results where a post has a specific meta key-value pair, namely, the meta key "featured" with a value of "true".

### User Story
When a user performs a search and a post with the meta key "featured" and value "true" is part of the search results, a badge indicating that the post is "featured" should be displayed next to the search result entry.

### Requested Features/Modifications
Ability to detect posts with a specific meta key-value pair in the search results.
Display a badge or indicator next to such posts in the search results.

### Additional Context
This feature enhancement would provide users with an intuitive way to highlight and promote specific posts in their search results, increasing user engagement and enhancing the user experience.

ZD ticket: 7174530-zd-a8c

Start by locating the Jetpack Instant Search search-results entry point and checking how post meta is exposed during result rendering. Define how the “featured”/“true” pair is detected and where the badge belongs, then verify that matching results show the badge and non-matching results do not.

Written by the indexing model from the issue text.