Add magic capable (un)register functions

[drashna]

Description

Adds support for "magic" processing of the (un)register_code(16) functions.

This is useful if you want to have the automagic handling of the keycodes, so that it swaps out modifiers or the like.

These functions will operate like a normal key, so it's possible to disable GUI keys, for instance.

Types of Changes

• Core
• New feature
• Enhancement/optimization
• Documentation

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).

[stale]

Thank you for your contribution!
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[Erovia]

Some documentation would nice.

[drashna]

closing since tap code functions are weak, now.