Menu key for open context menu might be hard to identify

[jwunderl]

Describe the bug

I don't think I've personally ever touched this button on a keyboard intentionally / recognized it exists, and surveying the keyboards in immediate view, 1 has the key where it's "expected" after i searched for what the key is supposed to be (to the left of right control), one has it hidden behind holding function key and a button squirreled away above the numpad, another holding function key to override the 'copilot button' back to menu, and fourth just does not have it as far as i can tell. Supporting it is good but my suggestion would be to make a 'normal' key work as well, and have that listed as primary option for it on the keyboard controls doc

[microbit-matt-hillsdon]

This was an unintended consequence of Blockly adding the menu key in addition to the Ctrl/Cmd+Enter that is documented in this slot in live. This open PR fixes it.