Can't minimize Riot app on macOS using standard keyboard shortcut

On macOS, ⌘+M is a reserved shortcut for minimizing any window. To many users, It's a very familiar shortcut. The riot app hijacks ⌘+M and uses it for enabling/disabling Markdown editing in the compose window. I suggest replacing the shortcut with something like ⇧+⌘+M.

First confirm that this macOS behavior belongs in this repository, whose description identifies an iOS app. Then locate the compose-window Markdown shortcut handling and verify that replacing ⌘M preserves Markdown editing while allowing the native minimize shortcut to work.

Written by the indexing model from the issue text.