Update README.md

[cron410]

Added tip for configuring the speedtest.

Description

Related Issue

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Chore (non-breaking change that does not add functionality or fix an issue)

Checklist:

• [ ] I have read the Code of Conduct
• [ ] I have updated the documentation accordingly.
• [ ] All commits are GPG signed