Adding custom keymap for Quark keyboard

[pezhore]

Description

Similar to my keymap for the Preonic, this brings a custom keymap to the Quark board. Of note, I've made the Fn layer's bottom row the number row - while waiting for more keycaps I salvaged what I could from a Filco keyboard and liked being able to see which keys were the numbers/special character keys (bonus points for the angle of the normally top row keys fitting nicely with my thumbs).

Types of Changes

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

Checklist

• 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.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).