API alterations to allow injection of hotkey parsing and event processing

I think a useful migration strategy would be to allow serialization/comparison to be overridden as part of the API.

When we talk about what this library does that is "novel" (as in, something you cannot reasonably achieve in a few LOC locally) the library does three things:

• It manages many shortcuts by implementing a Radix Trie.
• It manages event listening & dispatch avoiding footguns: for example delegated events, ensuring hotkeys aren't fired on form fields, etc.
• It provides the above with a simple install/uninstall API to simplify adding/removing event listeners and state from the Radix Trie.
• It comes up with some lose specification of how to expand/compare hotkey strings to decide when to fire a hotkey combo.

The last one is what causes us a lot of trouble and causes some trashing in this library. radix-trie.ts hasn't been touched in 9 months, prior to that 2 years ago. I'd say radix-trie is "feature complete". Meanwhile hotkey.ts has a regular cadence of alterations every few months as we reach edge cases and scale our use of this library.

The chief problems with the serialization format are:

• It is a psuedo specification. There's no formal set of possible values or a well defined grammar or spec. It is an ad-hoc grammar using RegExps. While this works fine for the most part, it is a source of bugs and confusion, as well as differences of opinion.
• It doesn't properly encode all of the state about what we as developers intend shortcuts to be. We've discussed this quite a lot synchronously; the concept of "logical" (WSAD) vs "Semiotic" (?) shortcuts.

Effectively the serialization of these shortcuts is, what you might call, unsolved. So I say let's make that apparent by allowing it to be overridden in the API.

The current API is as follows:

export install(element: HTMLElement, hotkey?: string): void {}
export uninstall(element: HTMLElement): void {}

I propose we expand this to the following:

export type ProcessHotkey = (hotkey: string): string[][]
export type ProcessEvent = (event: KeyboardEvent): string

export class HotkeyManager {
  constructor(
    processHotkey: ProcessHotkey = expandHotkeyToEdges, 
    processEvent: ProcessEvent = eventToHotkeyString
  )

  install(element: HTMLelement, hotkey?: string): void {}
  
  uninstall(element: HTMLElement): void {}
}

const defaultManager = new HotkeyManager()
export const install = defaultManager.install
export const uninstall = defaultManager.uninstall

By making a class, we can define custom processing for shortcut keys which allows users to define their own shortcut models, but also allows us to make more breaking changes behind experimental APIs, and even feature flag them. By still exposing the install/uninstall functions per the existing API, we ensure backwards compatibility which minimizes breaking changes, and allows us to "make the hard change easy then make the easy change". A 2.0 change could effectively swap the default hotkey functions out for the newer API, as a one line change.

Thoughts @github/ui-frameworks?

先阅读 hotkey.ts 和 radix-trie.ts，然后将当前的 install/uninstall API 与提议的 HotkeyManager、ProcessHotkey 和 ProcessEvent 接口进行比较。确定如何在不更改现有 default exports 的情况下集成自定义序列化和事件处理；当 API 设计和兼容性行为达成一致并完成实现时，即视为完成。