Add keyboard buff75

[Vem-596]

Description

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• [x ] Keyboard (addition or update)
• Keymap/layout/userspace (addition or update)
• Documentation

Issues Fixed or Closed by This PR

Checklist

• [x ] My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• [x ] I have added tests to cover my changes.
• [x ] I have tested the changes and verified that they work and don't break anything (as well as I can manage).

[Vem-596]

Some changes have been made, please help me review them, thank you. @zvecr

[drashna]

As of August 26, 2024, qmk/qmk_firmware is no longer accepting VIA-enabled keymaps as these have now transitioned to a repository under the VIA team's control.

As you've submitted a PR containing via or VIA-enabled keymap(s), this is your notice that they should be removed from this PR. You should now submit a secondary PR to the VIA QMK Userspace repository with your associated via or VIA-enabled keymaps instead.
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