* refactor: improve menubar keyboard accessibility
* fix: create a temporary widget for tray icon context menu
* fix: focus menu bar with Alt when autohide is off
* fix: make menu bar focus work more like the native menus
* fix: only focus menu bar if it's not already focused
* fix: track accelerator registration to avoid duplicates
* docs: add docs for & notation in app menu item names
* fix: only try to activate accelerator if it's registered
* fix: add friend to monitor window focus change
* style: add <memory> include
Sometimes the MenuHost would crash when the window is closed, the author
didn't recommend using MenuRunner on stack, but since we always run the
menu synchronously, this is no problem.
