Feature: Switch from deprecated keyCode to key in internal onKeyDown handler

[noahnu]

keyCode is deprecated (see https://w3c.github.io/uievents/#legacy-KeyboardEvent). As "keyCode" is officially deprecated, lexical should be updated to replace all references to keyCode with either KeyboardEvent.code or KeyboardEvent.key where applicable.

One of the functions using the deprecated keyCode:

lexical/packages/lexical/src/LexicalEvents.ts

Line 992 in ac97dfa

function onKeyDown(event: KeyboardEvent, editor: LexicalEditor): void {

What's the impact? The popular @testing-library/user-event package no longer sets "keyCode" on their synthetic keyboard events.