Feature Request: Support Shift-F10 to invoke right-click context menu

Apologies if this is a duplicate. I searched and couldn't find an existing issue.

Unfortunately, macOS doesn't natively support invoking the right-click context menu from the keyboard as is possible with the menu keyboard button or SHIFT-F10 on Windows and Linux. The solution associated with the accessibility feature to invoke CTRL-5(number pad) is insufficient because it opens the context menu where the mouse pointer is, not where the text cursor is.

However, third party applications such as Eclipse and IntelliJ on macOS do support this feature with custom application code. Eclipse implemented such functionality in this bugzilla: https://bugs.eclipse.org/bugs/show_bug.cgi?id=219305

This feature request covers adding this functionality to MacVim via the SHIFT-F10 keyboard combination. To be clear, the behaviour is to open the context menu at the keyboard arrow key cursor location, as opposed to the mouse cursor location. For example, this means when moving a keyboard cursor over a misspelled word, the context menu will display with, among other things, suggested spelling corrections for that word, irrespective of where the mouse pointer happens to be.

该 issue 没有指出源文件、测试或入口点。首先定位 MacVim 对 Shift-F10 的处理以及现有的上下文菜单调用，然后跟踪键盘光标位置是如何确定的。完成标准是：Shift-F10 在键盘光标处而不是鼠标指针处打开上下文菜单，包括对拼写错误的单词也是如此。