Improve public API docs

[EchoEllet]

Updates the documentation and Javadocs to make it more user-friendly and simplify integration with Controlify by:

• Updating outdated references.
• Adding Maven/dependency code snippets and the full file name dev.isxander.controlify.api.entrypoint.ControlifyEntrypoint to make it easier for NeoForge users to create in their IDE or terminal.
• Documenting how to register a custom radial icon.
• Clarifying the differences between onControlifyInit and onControlifyPreInit to resolve common confusion.

Related Issues

• Fixes Controlify Bindings API docs is outdated or invalid #696