changed casing on contributing.md

[KennyNeal]

Type of Change

• [ ] Bug fix (non-breaking change, fixes # )
• [ ] New feature (non-breaking change, adds functionality, fixes # )
• [ ] Breaking change (affects multiple commands or functionality, fixes # )
• [ ] Ran manual Pester test and has passed (.\tests\manual.pester.ps1)
• [ ] Adding code coverage to existing functionality
• [ ] Pester test is included
• [ ] If new file reference added for test, has is been added to github.com/dataplat/appveyor-lab ?
• [ ] Unit test is included
• [x] Documentation
• [ ] Build system

Purpose

The link to CONTRIBUTING.md in readme does not work on GitHub because the case is incorrect (all lower vs CAPS)

Approach

I've changed the casing on the link while leaving the file itself alone.

Screenshots

[potatoqualitee]

merci 😊