Add missing Manchester picture

### Link to the page

https://codeyourfuture.github.io/github_issues_prs_practice/

### Steps to reproduce

1. Navigate to the website
2. The image for Manchester on the second row is missing

Open the linked GitHub Pages site and inspect the second row of city entries to confirm the missing Manchester image. Find the HTML or image reference responsible for that entry, restore the missing picture, and verify that it displays correctly on the page.

索引モデルが issue の本文から書いたものです。