Add core documentation.

[nic-starke]

The following documentation needs to be added:

Wiki

• Project overview and goals.

• FAQ

• Download/Install Guide

• Development

• Scripts.

• Formatting / Style guidelines.

• .devcontainer explained.

• Cross-compilation.

• Flashing.

• CI/CD workflow.

• Testing

• Firmware Features

• Design process, decisions, tradeoffs, etc.

• Implementation.

• Review.

• Features that were removed.

• RTOS.

• Custom networking protocol.

• CBOR serialisation.

• Sysex transport.

• AVR Development

• AVR GCC

• AVR LibC

• AVRDude

• XMEGA

• Pros/Cons

• Desktop/Standalone Configuration Editor

Source Code

• Cleanup the existing in-source documentation
• Add more documentation and comments :)