fix: Show platform-specific keyboard shortcuts in UI (#6323)

Signed-off-by: Abhijay007 <Abhijay007j@gmail.com>

ui/desktop/src/utils/keyboardShortcuts.ts

@@ -0,0 +1,11 @@
+function isMac(): boolean {
+  return window.electron?.platform === 'darwin';
+}
+
+export function getNavigationShortcutText(): string {
+  return isMac() ? '⌘↑/⌘↓ to navigate messages' : 'Ctrl+↑/Ctrl+↓ to navigate messages';
+}
+
+export function getSearchShortcutText(): string {
+  return isMac() ? '⌘F' : 'Ctrl+F';
+}