Add an (ideally configurable) hotkey for opening the settings panel

[Hunter1]

Just add the ability to bind a hotkey to open the settings (about:preferences) panel. My preference would be `ctrl+,` as a default, but ideally this would be configurable by the user. 

[Jon]

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[tmgross]

I always find myself looking for a way to open settings without clicking, this would be a great addition.

Note that this does exist on MacOS, as cmd+comma. Using ctrl+comma on Windows and Linux is a fairly common equivalent, so +1 to that part of the suggestion as well.