macOptionIsMeta doesn't work for some keys in the US layout

[Eugeny]

macOptionIsMeta doesn't work for keys that produce composed characters, e.g. N, U and E in US layout

With Alt pressed, these are "dead keys" and trigger character composition. We need to find some way to distinguish between these Alt-initiated composition events and IME-initiated composition events when macOptionIsMeta is active.

This might in fact be as easy as ignoring composition when macOptionIsMeta && event.altKey