feat: add testenv to readme.md

[gap-editor]

Description

Notes to the reviewers

Changelog notice

Checklists

All Submissions:

• [ ] I followed the contribution guidelines

New Features:

• [ ] I've added tests for the new feature
• [ ] I've added docs for the new feature

Bugfixes:

• [ ] This pull request breaks the existing API
• [ ] I've added tests to reproduce the issue which are now passing
• [ ] I'm linking the issue being fixed by this PR

[gap-editor]

actually i didn't want to remove this part. so will fix it today. my bad.

[luisschwab]

@gap-editor can you fix this?