CLI: Add basic json keymap support

[Erovia]

Description

This intends to be a groundwork for better/more json keymap integration.

Types of Changes

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

Issues Fixed or Closed by This PR

Checklist

• My code follows the code style of this project.
• 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).

[skullydazed]

To document what we talked about on discord a few days ago, I would like to see this done as part of a usecase rather than add it on its own without features to hang on it.