Lighthouse requirement score

### Link to the page

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

### Steps to reproduce

Lighthouse score is less than required.

Start by running Lighthouse against https://codeyourfuture.github.io/github_issues_prs_practice/ and record which audits fail. The issue does not name a file, failing audit, or required score, so confirm the threshold and expected fix with the maintainer; done means the page meets that requirement.

索引モデルが issue の本文から書いたものです。