Add Custom Keybind Detection for Datapacks

Currently, Minecraft Java Edition allows datapacks to detect certain player inputs, such as jumping, sneaking, sprinting, and movement through predicates. However, there is no way for datapacks to detect arbitrary keyboard inputs, such as pressing the C or V keys.

I suggest expanding the existing input detection system to allow datapack creators to detect custom keybinds without requiring client-side mods.

Ideally, datapacks could define custom actions that players can assign keys to in Minecraft's Controls settings. These actions could then be detected through predicates or advancements, allowing functions to execute when a player presses or holds the assigned key.

This would open up many possibilities for datapack creators, including custom abilities, combat mechanics, spellcasting, interactive menus, and other gameplay features.

These custom keybinds should work independently of existing Minecraft controls, allowing players to use additional inputs without sacrificing vanilla functionality.

Adding this feature would significantly expand what is possible with vanilla datapacks and resource packs while maintaining Minecraft's accessibility and customization.