[MacOS] `⌘M` for Minimise should be respected

[whisperity]

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Contour's frontend doesn't properly respect the ⌘ Cmd-M keybind which is universally used to minimise a window to the dock. There is no Minimise keybind action. This whole thing is strange because the normal window-decoration created by Mac, when clicking the yellow button, actually does the minimisation in the usual way.

Interestingly, ⌘ Cmd-H for hide works perfectly. And the green full-screen button and the ToggleFullScreen keybind also do the same thing.