feat(keyboard-shortcuts): add alternativeShortcutKeys config for layout-independent shortcuts

[iospro]

Problem

On non-QWERTY keyboard layouts (e.g. AZERTY, QWERTZ, Cyrillic) the physical keys produce different characters, so existing single-key shortcuts (like A, V, C) stop working correctly — the keypress event delivers the layout-specific character rather than the intended one.

Solution

Add an alternativeShortcutKeys config option that maps alternative key codes to their primary shortcut equivalents. When a keydown event doesn't match any registered shortcut directly, the handler looks up whether the pressed key has a primary mapping and dispatches that shortcut instead.

Changes

• config.js — documents new alternativeShortcutKeys option: Array<{ key: string; alt: string }>
• configType.ts — adds TypeScript type for alternativeShortcutKeys
• configWhitelist.ts — allows alternativeShortcutKeys to be overridden via configOverwrite
• keyboard-shortcuts/functions.ts — adds getPrimaryShortcutKey(state, altKey) selector
• keyboard-shortcuts/actions.ts — extends keyDownHandler to resolve alternative keys before shortcut lookup

Usage

// config.js or configOverwrite
alternativeShortcutKeys: [
    { key: 'A', alt: 'Q' },  // AZERTY: Q physical key → A shortcut
    { key: 'M', alt: 'µ' },  // macOS option key variant
]

[jitsi-jenkins]

Hi, thanks for your contribution!
If you haven't already done so, could you please make sure you sign our CLA (https://jitsi.org/icla for individuals and https://jitsi.org/ccla for corporations)? We would unfortunately be unable to merge your patch unless we have that piece :(.