Update img-tools.md

[Alonso287]

Description

Starred Photopea because of its powerful functionalities and its similar layout to Photoshop, while being free (it has an optional paid subscription, but none of its features are locked in behind such paywall)

Context

Types of changes

• [ ] Bad / Deleted sites removal
• [ ] Grammar / Markdown fixes
• [x] Content addition (sites, projects, tools, etc.)
• [ ] New Wiki section

Checklist:

• [x] I have read the contribution guide.
• [x] I have made sure to search before making any changes.
• [x] My code follows the code style of this project.